On my Desktop my browser use is as follows:
I use Firefox/nightly(64 bit) 90% of the time.
My wife uses Chrome 90% of the time.
The other 10% used to go to opera, but after this latest installation of windows rather than uninstall IE, I left it on, updated to IE9 and use it for that other 10%
I have a fairly powerful home-built PC and a 50Mbps internet connection. To be honest, I see very, very minimal differences in speeds in each of the browsers, other than firefox taking slightly longer to load initially.
One of the biggest differences I notice when browsing is Flash/Java. Nightly (firefox 64bit) DESTROYS the other browsers in terms of loading flash and Java based sites. One of the best examples would be to go to google maps, satellite view and zooming in and out quickly. With Nightly, it is just soo much smoother and fluid than its 32 bit counterpart.
Now on to IE, the 64bit version is so unstable compared to the 32bit one, it is unusable at times. There is no (easy) way to make 64bit the default browser. Sometimes it just hangs while loading pages, etc.
So what I would really, really like from IE10 is better 64bit support. Hell, if you aren't releasing it for XP, why even bother with a 32 bit version anymore? let IE9 serve those still stuck in 32bit land.