Just got an invite a few days ago. Played quite a few games last night. I would say it's coming along well - and certain parts definitely have that trademark Blizzard polish, others definitely need some.
I like it, I want to play more but I'm not sure it will hold my interest for an extended period. I really only played LoL because my friends did and I'm not sure any of them got an invite no bonus party XP for me.
I do like some of what they've done (team XP, no items) to try to at least mitigate the whole snowball effect of getting behind early. You can still lose hard if you do, but it's less damning. Good direction to take imo.
Lots to like, but I also hope some of the "man that's annoying" bits are a result of alpha. Or maybe I need to check some settings to change them lol.