Well XP is more tweakable than Win2K. I hate WinME I think it is a POS. I love Win2K, but XP is so much more. All the fancy UI stuff can be turned off, even some of the UI tweaks that were added back in Win98 can be turned off, like the Gradient on the title bar of windows.
As for the Multiple IE windows thing, its not just IE it is any app with allot of windows open, like Outlook, but if you don't like it... turn if off.
Allot of what MS seems to be trying to do is increase out of box experience, make the features that were always there, but could only be got to from the registry or should been there, accessible to all users, from the newbie to the advanced and even the know it alls (who actually do know jack).
Who here has WinME and had to search a site to turn off that damn system restore? Well now there is just on check box to turn it off.
Since Win98/EI4 added the web content in folders I always turned it of for performance, but in XP I have found that the little side bar actually suggests some useful tasks. Saving me time.
XP will be the OS of all users, the newbie will love its hand holding and the expert will turn off all the hand holding and may even find a couple new features that make the upgrade with the money.
The coolest feature for me since I build computers for my relatives who live as far as a 1000 miles from me, is the Remote desktop assistance. This will save me hours on the phone with my mom thing to walk her through installing that new program or any of the other 20 reasons she might call me up saying "help!"
When XP is released allot of you will be surprised.