"Aero Peek, which displays a full-screen preview of an application before you switch to it,"
Eeek, that sounds terribly annoying. Perhaps it will be better than it sounds in practice.
"It depends [...] on what Microsoft calls online IDs"
In other words it is infected with some with some manner of user controlling DRM. No thanks. There are open source equivalents that dont you require users to give all their base to Redmond.
"In the beta, you could drag a folder to Libraries in Explorer and it would automatically be added as a new library. What you then have is a link to that folder in a central location[...]. Microsoft then figured that some users would not appreciate the difference between links and copies and would delete the original folder, thus losing their stuff"
Good greif, are Windows users really that dumb? No wonder Windows is so bloody nannying all the time.
"If you try to add certain kinds of network drive to your library, such as a Linux appliance stuffed with MP3 files, you get a bewildering message stating that the drive cannot be included because it is not indexed."
Well, colour me shocked. A Microsoft product that doesn't play well with other peoples products, who woulda thunk it? Microsoft are the software equivalent of Sony really.
"Underneath, Windows 7 is mostly the same as Windows Vista, but it is an unequivocal improvement."
Really? It sounds like it would be more ethical to release it as a Vista Service Pack instead of making Wintards go and buy it again after just having been gypped with their Vista purchase.