I have been using this new version (4) of Firefox for a little over a week on both my pc and mac. I love the streamlined interface w less space lost (aka more efficient use of) above your actual browsing space. On the computer(s) side, I love the integrations with yoono, evernote, readit, stumbled upon, etc. all with the fact that I can have them match on both platforms. I am looking forward to installing and trying out on my Incredible to see how well this all flows.
Regardless, both ie and safari have been relegated to the background for browsing unless an installed app triggers them. Firefox and Chrome (or more importantly Flock's version of Chrome) are far superior browsing platform choices and I think that is the key, they are platform choices.