I started using the nightly builds of v.3.0 before even Beta 1 was released. The final 3.0 is much better that 2.x, it is much faster, it also has a host of new usable (keyword is usable) features and has a much smaller memory foot print. Frankly, I only use IE to test and for monthly patches, and even then I feel like I'm standing still with it slugishness.

Tried Opera a couple of months ago. It was a lot faster than the old Firefox, but there were some limitations when I tried to get it to work with other software, especially torrents and DNN. So I deleted it again. I would guess that Firefox 3 is just as fast and easier to use, unless Opera have a new version out too.