Can't really answer the poll as my option ain't there.
I use IE6, as that's the one installed on the library computers.
I do, however, install the Windows Live Toolbar via Windows Live Messenger.
I personally like the toolbar, as, like Chris mentioned with IE7, you can use tabbed browsing instead of multiple windows which can drain the computers resources so easily. Right now I've got two tabs open; APi plus another tab, currently in the background which has my hotmail account open.
Anyway, what was I saying? Oh right, I don't know exactly what IE7 is like, but I certainly like the live toolbar which is an IE6 feature created to kind of *mimic* IE7.
Er, that's all...