I tried Opera, IE, Chrome, and Mozilla, ALL latest versions. And believe me, Mozilla- the Best. 
It's faster. 
And hotter. 
For me, the order is:
1. Opera - The interface and ease of use amazes me. Together with opera turbo in slow connections. But the startup time is a bit high on Windows XP. For windows 7, its fast.
2. Google chrome - inherently faster.
3. Mozilla Firefox - Causes problems when a lot of tabs are opened. Cookie handling is not as sophisticated. I've never tried any addons though. So, can't comment on that. But I find it a bit slow.
4. Internet explorer - Too many security warnings and hassles.
