I also noticed performance differences using Chrome but it wasn't that much of a difference so Firefox is and will always be my #1. Firefox 3 does have JavaScript performance issues on my computer (only 1ghz) but they said JavaScript performance will be increased in the 3.1 version so as usual they always fix the parts I dislike about Firefox (hated the memory leaks in Firefox 1 => they greatly improved it in Firefox 2 and even more in Firefox 3, I hated the slow starting of Firefox 1 => Firefox 2 started much faster and Firefox starts blazing fast!, Bad JavaScript performance in Firefox 3 => Will be improved in Firefox 3.1 without a doubt). There goes my skepticism
Also, Google released a browser in order to provide even better targeted advertisements, luckily you can "disable" that now but I wonder if it really does disable Google's spying, which Google is known best of. Also, someone probably rang a bell at Google because of the popularity of Adblock with Firefox, this affects Google's main income, which is Adwords.
They said their browser will have add-on support in the future but I really doubt Google ad blocking will be allowed, I even dare to bet my brand new Ferrari (which I don't have) on it.
I used to be an Adblock user but I noticed that by using OpenDNS performance was better, with OpenDNS I can only block malicious ads (adware, etc.) which was my main reason of using adblock. Google ads do provide me with useful links from time to time.
For these reasons: Firefox is da best! (and Opera second best :p) (And darn spreadfirefox for not accepting my post regarding Chrome...)