I use Firefox, with Add Blocking on, as well as the Adware Block Plus(as well as modifying my hosts file). I have several friends who use neither, and frankly they slow the game down for all of us.
This wouldn't really bother me except that it also slows down people enough that they have to re-connect to stay in the game, which they can not always do, because the adds take so long.
I spend a lot of money on WGT which gives me an add free experience(along with my pop up and add blockers).
For people who don't spend a lot of money(which they may do in the future if they don't have problems with the time spent on advertising). This is a negative experience.
People can deal with a 10 second add, a whole minute is going to turn people off.