I'm using chrome on my laptop because chrome is lightning fast in terms of startup time and the laptop sucks so it needs as much speed as possible.
But for my regular use I can't go without my firefox extensions like gmail notifier, html validator, fireftp, flashblock, stumbleupon, etc etc.
I'll keep using it every now and then tho, if user supported plugins are introduced, as well as a couple of settings options, i'll change for sure.
someone mentioned firefox extension support. i wonder how hard that'd be, given that firefox is open source, and this is google we're talking about. they could probably whip up some sort of virtual machine that loads firefox plugins.