I've tested Chrome out on my main rig, but didn't switch from Firefox because my computer is fast enough that the difference between the two was negligible or nigh non-existent. Plus, I love NoScript (at the time of deciding between the two browsers Chrome did not have a NoScript equivalent, maybe it does now, I wouldn't know).
I DO use Chrome on my slower-than-Pangaea netbook, because Chrome is MUCH faster on slow machines than other browsers.
I used to use Opera, but some websites I regularly visited at the time did not cooperate with Opera, so I stopped using it.