just thought I'd share the opinion of a newcomer to the Fire Emblem franchise, the only other game I played was.. this one, using a NES emulator. I don't remember exactly in which chapter I am, but I just got Merric (and IIRC I turned the game off because I was going to lose one character that I didn't want to)
what do you usually do about losing characters? I have let one axeman die and I guess I had only one other unit killed. it kinda sucks having to restart some missions from the beginning but it's funny, unless the character is absurdly generic (e.g. the axeman), I don't wanna lose any unit at all! and I'd guess that it will be worse when the levels are higher, it will feel like that I lost a lot of time with them if I just let them die..
I don't know if it's fair to compare with Advance Wars, but I played a bit of Days of Ruin and I really didn't care much about the story (also when the scenarios started to feel really "scenario"-ish - that is, there wasn't really much strategy but rather doing the right movement - I stopped playing it). this one is the first Fire Emblem (I would expect that later FE had more "complex" stories) and it seems really cool gathering a lot of troubled characters to reclaim what is yours 
my "experience" so far has been pretty good, the game flows well, Intelligent System's interface is great, skipping enemy movement, etc. and while it's not shallow, there is not also a shitload of stuff to play with...