I love CM. I also think that FIAR is a quality, beautiful way to homechool and agree that you still use alot of CM methods with FIAR. I would definitely use FIAR for my dc if it wasn't so hard to obtain (due to shipping, availability of books etc as we are in Australia).
I think it is really important to do what feels good for your family and not feel confined to a method as such. As time has gone on we have used more and more of CM methods and advice, but I have had to let God lead us in our homeschooling because my children (our whole family) do not fit into one method (or box) of education.
Your children will learn and develop regardless of what they are using, if you are a parent who loves them and looks for what suits your family. To grow in a love for living books in those early years is priceless. If you are just starting FIAR would be a great way to help you get into the swing of things. There's a little more leg work choosing and carrying out CM, in saying that it is all very gentle, remembering to keep lessons short and bring them to an end before the child starts to feel fatigued with what they are doing. If you can end a lesson while they are still on a high and enjoying it they are more likely to get back into it next time with enthusiasm & without moaning! This is a lesson I've been learning the last 18months. My first child is really the guinea pig, poor thing.
We have a couple of FIAR books and occassionally look for the manuals (on sale) and would still consider using it down the track - and this from an avivd CMer.
Don't be afraid to be your own style. You cannot go wrong either way and variety is a wonderful thing.