But IE still won't conform to CSS standards.
Most of which Firefox had over a year ago. As for security, well, given how tightly woven IE is into Microsoft's operating systems (try getting an OS update without it), it's now too critical to be used for daily browsing. And of course, its security sins are considerable versus some of the minor things I've seen in Firefox.
I started out on NCSA Mosaic (that was after being around the Internet for about a decade), then MCC/Netscape. Switched to IE at version 3, then switched to Mozilla/Firefox about three years ago. Why would I want to switch back? Firefox does everything IE does -- except talk to Microsoft websites for their OS updates.
Tabbed browsing is great when you have a lot of regular search queries that you do on a regular basis, for eBay or Google or whatever. It's also dramatically more memory efficient -- I have some preset bookmark folders that instantly create more than 30 tabs. Can't do that to IE without crashing or thrashing.
Not all Open Software is "there yet", but Firefox and Thunderbird definately are.
Gotta love competition. Now the Mozilla folks won't get complacent.
# Support for XPSP2 and newer versions of Windows, including Longhorn, of course (sorry, no Win2K support)
Except for those on less than XP apparently, they don't have to worry about IE getting better. So if you're using 2K you have to buy a whole new OS you may not want if you want the newer IE.