First I'm going to the pros and cons and then I'll tell you what I think.
Let me just start off by saying that FIAR and Sonlight are NOT alike at all. It's like comparing apples with the oranges... One is a literature approach (Sonlight) and the other is a unit study approach (FIAR). So that right there should tell you whether it will fit your style of homeschooling or not. so...
pros: Unit Study approach that is very open ended and simple. It is set up that each day you read the book than do one of the subjects (Mon- Social Studies, Tues - LA, Wed - Art, Thurs - Math, Fri- Science as an example) It can be beefed up by adding additional chapter books as read alouds and writing assignments, copywork or research. There is easy (read doable) hands on projects but the majority of the subjects can be done verbally. Its takes about 15 to 30 minutes a day to do. You will need to add a Language Arts program or Phonics (or both) and Math, so that would basically be the 3R's. It does not teach ancient history or really any history. Now for you this may be a con but not for me. I don't see any reason to teach children of ancient cultures when they don't have a very good concept of time...period...as in ancient history was what we had for dinner last night. Also most ancient cultures had a system of religion and other topics that don't really sit well with my belief systems so I don't feel the need to "show" that stuff to them at this age. In other words I feel that a lot of ancient history is age specific and usually a better topic for High School or at the very least Jr. High. Planning* is easy for me because I use a sticky note system in the book that makes this easy. I do my sticky notes once a year in summer and I'm done planning. It takes me about 2 hours total. FIAR is very affordable for the early years...as in you buy the Volumes at $35 and you can reuse them for several years. You should be able to find *most* of the books at your library but several of them are out of print (OOP) so you'll need to utilize the ILL at your library. A lot of the moms end up buying most of the books and that's about 130.00 per volume which would be $35 + $130 = $163 per volume. Each volume is about 1 semester of work and there are 4 Volumes in the younger years. Volume 3 is really nice for summer and that was it's original intention but you could use it otherwise. Volume 4 in the series is really for older children who are almost ready to read chapter books so about 8-9ish. That would leave you with Vol 1-3 for the entire year. Most of the critics I've seen think that FIAR is only a Kindy program because they don't realize you can rerow ( do the unit again) the books. Because your child will be at different developmental abilities each year you can pick something different the next time you rerow the book to discuss.
cons: Planning* as with a lot of unit studies can be daunting especially if you are adding in lots of lap books, notebooking and other things that are not in the Volumes. I say this because it seems like everyone adds tons of this crafty stuff and makes what was once a simple idea into the Mt. Everest of unit studies. There are many people that feel without adding these things that the unit isn't complete or "enough". You'll see a lot of questions about whether it's "enough" on the official FIAR board. If you live in a state that has testing on Social Studies and Science with a set scope and sequence they expect taught this could prove to be a problem, however I don't live in one of these states. FIAR doesn't go to high school or in some cases even Jr. High so if you like the idea of having that all mapped out for you that won't happen so you'll need to change programs. FIAR doesn't have the ideas under the general topics (SS, LA etc) organized by age appropriateness. So you don't have it graded as easy (4-5yo), moderate(6-8yo), hard projects(9-10) which *I* think would make it easier for beginners to get the hang of. You have to just figure out what your kid is capable of. Some of the books don't seem to have a lot of activities to choose from so they might not be of interest for rerowing.
Pros: BOOKS! If you love seeing books on you're shelves you've come to the right place ;) It's a Literature based history curriculum using some of the best modern literature around. Sonlight is ALL laid out for you, so NO planning ---this alone can sometimes can outweigh ALL the cons. For many burned out moms this is a great weight off their shoulders. Great Missionary biographies are included as is bible and as of last year LA, however my understanding is that most people don't like the LA. Because this is content only and not skills you'll need to add math, possibly LA and science. They do have a science core if you're interested in that. Sonlight can reasonably be combined with kids about 3 or even 4 years apart in some cases.
Cons: Price...seriously it's expensive but there are ways around this. For me spending this kind of money on something that's not on the SAT isn't worth it but again there are ways around that. You'll be reading A Lot of books. If you don't like reading aloud or lots of books this would not be the curriculum for you. In the age range that we're talking about I think the amount of books is fine but once you hit about Core C (3rd grade approx.) there is a LOT of books. There is no hands on elements if that's something your interested in. I know that when you read a good book to a kid they'll act it out or draw it so I don't see this as a problem but if you want a unit study this isn't it. You can of course add those things but it's not built in. Because this is driven by history some of the books just aren't that good because they have to fit the time period. It's easy to fix by just replacing the book but if you don't know how or what to replace it with that could be a problem. If you don't like the time period that's being studied...too bad...you're mucking in it for the whole year or in some cases two years. You may need a core for each kid and that can be expensive. The assignments in the IG can be choppy meaning you are reading several different books everyday. For some kids (and moms) this is really annoying. You can get around that by assigning each day of the week one of the subjects like you do in FIAR. So on Mon - History, Tues - Science, etc. or...you could just read the books without stopping....like we have ;^) They rely on Usborne books a lot which some parents love and others absolutely despise so if you're really CM influenced you'll in most cases need to replace the science and in the lower grades quite a few of the history spines. Speaking of history it starts off Core A in ancient history which is a big thumbs down for me based on what I wrote above.
Okay so what do *I* actually think? Let me say that I believe in self education a la Robinson, PACES, URtheMOM.com so that really colors my thoughts about mom having to run around like a chicken with her head cut off for non-skills stuff (meaning not the 3Rs which I've stated before is what's tested for on SAT's). If you want to know what I really think then read Are You SURE You Have The Right Curriculum by Renee Ellison over at HomeschoolHowTo's. Renee's book Teachers' Secrets and Motherhood Savvy for Homeschoolers should be mandatory reading!
So first off you can print off the free Three Weeks of an IG of Sonlight and actually do it for a couple of weeks and see if it's what you're looking for. The Core 3/4 and Core K books are definitely worth getting for this age range. You can reread them over and over for your kids and enjoy them for years. FIAR is a cheap investment and you can easily get the Vol 1 (even on ILL from the library) and see if it's what you would like. Here is a sample of Ping from Vol 1 So that's what I think...try before you buy if you're going to pay that kind of money. If you enjoy unit studies than FIAR is fun and it's REALLY easy to add (as long as you don't go crafty crazy with it) to. I have 7 cores of Sonlight and I'll say that I mostly use it as a booklist and to stock my home library. However with that said I personally don't like about 1/4 or more of the books starting at about Core A so for *me* I wouldn't want it to be my only curriculum.