Here are my 4 sites I use for betting:

Fairlay  5.0  
+++ best odds on the market
+++ very high limits
+++ Exchange
++ good support
++ instant cashouts (small amounts)
-- extended sportsbetting is quite new
- no instant deposits
- not so much markets, but everything important is covered

Nitrogensports 4.0
+++ awesome interface
+++ instant deposits + cashouts
+++ good support
- odds are not the best

Cloudbet 4.0
+++ trusted player
+++  many markets
-- odds are sometimes not competitive

Betcoinsports 4.0
+ acceptable odds
- interface is improvable