Like many I was a long time FF user due to it's extensions - many but particularly Tab mix Plus and Download Them All (and Adblock but most have that now)
FF has slowed whilst Chrome is fast and I am a heavy Google user anyway so ...
Have consider Chromium and SRW Iron but not that concerned about privacy as I am Google's b1tch already
My major gripe with Chrome is the stealing of focus
With FF (and Tab Mix plus) I could use Tweetdeck or an email program and click web links which would load in tabs in the browser in the background without stealing focus from the current app
Would love to have that capability from Chrome but not possible
Does Opera do this? If so I might give it a try