Note that there is a recently added web service that let's you edit, add, manage bookmarks on .Mac via the web: http://bookmarks.mac.com
I use the backup feature to always backup my current "hot" project.
I use the instant picture publishing feature of iPhoto. Huge time saver that. Upload images to iPhoto; select images; publish. Done. Pictures available on the Internet.
I use HomePage to edit my movies and photos pages. I have gobs of these and HomePage helps me easily keep these pages organized quickly w/o any manual file editing. Perfect when you have baby and grandparents.
I use iSync to sync my Address book, Calendars, and Bookmarks
I find the iDisk plenty fast enough; maybe this is because I have solid broadband service through RoadRunner. I routinely share files by dropping them in my Sites folder and emailing URLs. I could have done this w/o iDisk, but I've found before it was just tedious enough that I would use MIME attachments instead. Now instead of sending big files to dozens of people, I always send URLs. It's just as easy to drop a file in Sites as it is to drop it in my email message; but much less download pain for my email receivers many of whom still use POP.
I love having IMAP mail! And The .mac email client just blows away the HotMail web client that I had been using (in terms of clean design and ease of use).
Finally I use the Sites folder on my iDisk to host my own web sites.
So I guess I use enough of .mac to make the 8 bucks a month a very good value. I think if people really valued their time, they would easily come to the same conclusion.