Ironically, I still use the DOS shell (command prompt, to be technical) a lot to this day, in both XP and 7.
I STILL have not found a way to replicate the accurate and functionality of the Windows XP folder search in Windows 7, when searching for text in files. I'm almost certain I tried indexing, not indexing, trying to force, trying to find options, etc.
In XP I could just say, search for files with XYZ in their title, or files with XYZ in their contents. In 7, to catch 100% of such files, as far as I know I'm better off just bringing up a DOS prompt and using "dir /s *xyz*" or "findstr /s xyz *".
That sort of feature regression makes me sad from XP to 7, and I'm someone who LIKES Windows 7 (and who used Vista for a fair bit, and did NOT like Vista).
For another example, with the Windows 7 calculator, certain things are locked in the programmer view, and certain things are locked in the scientific view. As far as I know, the only way to get numbers between them is to store a number in memory, change modes, recall the number from memory, and keep working. In XP, it was an immediate seamless step to use the features that are now mode-restricted, since you didn't have to change modes, unless I'm just totally forgetting something.