It looks as if Myspace is strongly encouraging people to upgrade their browsers to either Internet Explorer 7 or Firefox.
Now I must admit I'm not a huge MySpace user also I use primarily IE6 for my work from home and save IE7 and Firefox for my time in the office where I would lean more to being an early adopter than at home.
When you log into MySpace with IE6 you get the following "MySpace recommends upgrading to IE7" screen shot:
MySpace hits you again if you attempt to use their new Profile 2.0 tool.
If you look closely at the two screen shots it appears MySpace prefers FireFox over IE7. The IE7 recommendation from the opening screen is actually an advertisement and the Profile 2.0 tool is a true Firefox recommendation.
So will it speed up adoption? With Myspace's millions of users I can't see how it wouldn't - I'm actually writing this from home using IE7 thanks to MySpace's recommendation.