“Please note: We do not recommend that anyone other than developers and testers download the Firefox 3 Beta 1 milestone release. It is intended for testing purposes only.”
Alright, with that aside, I feel that the new Firefox loads many times faster, as well as looks better. Even though I have only used it on my mac, I think that it will look good in the vista/xp environment as well. Most of my favorite add-ons haven’t been updated for firefox 3, so my colorful tabs and other such tweaks aren’t there, but it is something I am completely comfortable with.