I'm really on the edge about purchasing FE:A. I assume you'd recommend it?
I would, but it depends on what games you like. There's a free demo; I recommend downloading that to at least get an idea of how the battle system sort of works. I say sort of because important elements aren't available in the demo, such as support conversations to increase pair-up bonuses (I'm not even sure characters can pair up at all in the demo). But still, would give you an idea.
I was on the fence about it for a few months. The only FE game I'd played before was Shadow Dragon, which I liked in some regards, but ended up quitting a battle or two before the end because I was trying to keep everyone alive, and there was a battle full of archers where you pretty much accept a death was going to happen. FE:A is quite a bit more forgiving.
For me, I like that it's mostly strategic. Unfortunately, if you know some tricks, you can break the game, but that's not normally an issue on a first playthrough. It;s also fun to match up characters; and most of the characters are surprisingly likeable. Seeing differences in who you make into your team keeps me coming back and there are a number of sidequests I've never done despite having around 200 hours clocked on my 3DS. It's number 2 behind Shin Megami Tensei IV, though I have a feeling both will be dwarfed by Super Smash Bros 4 when it comes out. It's ... kind of sickening how much SSB I'm willing to play without end.