Anonibet - 4
Been around for a long time and led the way for everyone else, so have to give them credit for that. They've got a pretty complete offering (with live betting), though their odds aren't very competitive and it doesn't look as though they're putting a lot of effort into improving their product - it's a pity as they are getting left behind a little bit.

Cloudbet - 5
Their odds are as good as any going, they've got the best live betting out of anyone, their limits are very high (not that I ever come anywhere close to them), they've got the best mobile site by a mile, and they're pretty consistently updating their site and adding new features. The only thing they're missing is live chat.

Nitrogen - 3
They do pre-live very well, with odds as good as Cloudbet and fairly high limits, however without live betting no site should bet any more than a 3 in my opinion - this is such a standard feature in online betting now, there's really no excuse not to have it.

Directbet - 1
I like that they're innovative and taking advantage of some of BTC's inherent properties to create a very unique product, but the way they clearly must encourage people to post positive revues (not sure how, I guess maybe it's a condition of getting the prize for their prediction contests) is ridiculous. Got to give them a 1 to cancel out at least one of those bogus ratings.

Jetwin I haven't tried, it looks OK, but have read that they're pretty open about cutting limits for winning bettors, and I've also read of them stiffing players in the past claiming that they were pros (even if they were, it's not an excuse to cancel bets they've already placed). Also they don't appear to offer live betting.