I am using Firefox at the moment, and have Comodo Dragon as a back up. I keep these two exclusively for WGT. Maybe it doesn't matter that much, but that is how I do it and it keeps me amused !!
I really think that one browser is no better than another, its what is best for the computer you have. We see many posts from people complaining their meter is bad and all that stuff. Thats nothing to do with WGT its generally on their end, and getting the right browser for their computer is just part of the process of improving the meter, there's a bunch of other stuff too.
Bit of topic, but having a rant !!