I upgraded from my 3GS to a Lumia 710 at the weekend - liking it so far as well. App selection isn't anywhere near as bad as I thought it would be, it's pretty good to be honest - more free ones than I thought too. Admitedly there are one or two missing that I used on my iPhone, but it' hardly make or break, as there are a few I'm finding very useful that are loaded on as standard.
I think they already put out an update to fix battery life? The 710's is fine, lasted me 1 day 3 hours so far, with a lot of usage as you'd expect for a new phone...I imagine it'll average out the same as my iPhone, which is fine.
Any apps you'd reccomend so far? I'd say Connection Tiles is a useful one for quickly turning off WiFi etc. without searching through the menus.