The new tabbed-browsing feature of IE 7.0 has one benefit I didn't expect - opening a new tab does not automatically bring that view up to the front of the display - so I can right-click/open in new tab a link in the middle of some page I'm reading, and not have to deal with the stupid computer bringing up that page when I'm not done with my current page.
Sadly, this feature is restricted to one aspect of one program. WinBlows assumes (wrongly) that any time I open a new program - email, word processor, whatever - that's the program I most want to be looking at and working on right now. Given the long load-times of many programs (particular offenders include PhotoShop 7.0 and Eudora 6.2), I might (usually) want to start a program up, but continue working on my current task. Frustratingly, my current task is usually interrupted by some half-loaded currently-unuseable thing that WinBlows mistakenly thinks I really want to look at. Typically, a half-loaded program doesn't actually cover the screen; instead, there may be a large white box in the middle of the screen, with aspects of my current task in the background, non-functional. Also, the mouse pointer gets converted into that fucking obnoxious arrow-with-small-hourglass design that is supposed to signal "working in background, you can still use your mouse" but actually signals "any input made during the next 10 seconds will be saved and applied to the not-yet-visible screen I'm busy slowly opening, with entertaining results".
What I'd really like in software design is an assumption on that part of the operating system that whatever I'm doing RIGHT NOW is the most important thing for the computer to focus on - any other programs also running (multi-tasking) or loading, or re-directing, are of lower priority for my attention. Don't pop them up on top of what I'm doing, don't flash the icon in the bottom bar, don't make sounds or present sliding, animated notices. I don't fucking care that a webpage has finally loaded; I'm busy writing a damn email.