I guess PrimeDice is overall top site if you are seeking flawless experience it is the place to go.
I also like FortuneJack - never had problems with their service.
Furthermore I saw some positive opinion of BetKing - but haven't play there yet.
EDIT: Recently I found 999dice.com - a dice site which is offering permanently 0.1% House Edge.
It turned out that 999dice might be not that trustworthy after all.