it's alright. IMO the whole game gets stale after a while and, well, it's just frustrating. Though I put in like 20 hours the weekend it came out. i don't really feel the need to achievement grind, and I for one only played on the "hard" mode that is in it. I only had vanilla before and not wrath of lamb, so it also gets irritating looking up what a million items do. But it's a better frustration than the original for me (I never beat satan in that, and it got boring to play through just for a chance to beat 1 boss. Now I just die a lot in rebirth, and also hope to get devil rooms so that if I win, I can go to satan. Now there are like bosses after satan, but I havent gotten those).
but, that being said, any sale of it is good. i'm sure i'll fire it up eventually again.