FF, IE9, Chrome, and now Maxthon. Maxthon has recently become my primary browser and I hardly ever use IE9.
I'm still using Sleipnir as my primary browser at home, and find it to be very stable. At work I use Chrome mostly, but right now I have had Sleipnir continually running for more than two weeks, and right now have 60 tabs open and it's running really well - much better than most other browsers would in the same situation.
I know it is dull, but I am just using one Browser, IE10. Are quite pleased with its performance and security.