I recently tried Vista and I must say I'm impressed. Sure Vista has its own faults, but there are many lessons for Ubuntu to learn from Vista:
1. Search which works: Vista has this amazing search capabilities which lets you search every inch of your PC ( thanks to the kick delivered by Google Desktop) and surprisingly 'It Works' every time you use it. It even supports natural language input like, "Show me Bob's email, sent yesterday". Ubuntu too has a software called Tracker. It is meant to track all your files and faithfully fetch them when you search for it. At least that's the theory. In reality Tracker rarely works. In my experience with 5 installations of Ubuntu, Tracker has never worked. I have tried each and every trick in the book to make it work, but it never even manages to retrieve even one file.Ubuntu, please make it work.
2. Backup and Restore: Vista and XP have this useful functionality by which you can restore your PC back in time, in case you muck things up. Sure, it does tend to restore even things like Virus and Trojan Horses, but most of the time it manages to do its work efficiently. In Ubuntu if you muck some thing up, its back to the basics (Installing the OS) . Ubuntu must have such functionality!

4. Disk Partition: Vista has an easy to use disk partition tool which makes disk partitioning a cinch! Since Ubuntu is used by a geeky crowd it seems odd that it doesn't ship in with a disk partitioning software.
5. Calendar: Most of us use calendar on a daily basis. I personally use Google Calendar and sync it with Windows Calendar. Ubuntu should include any decent calendar which can sync with Google Calendar.
6. Advanced Snipping Tool: Vista upgraded the lame 'Print Screen' function to include a robust screen capturing utility. Ubuntu has a not so option rich 'Capture Screen' utility. Ubuntu snipping tool only allows you to specify the time after which it will take the capture. Of course you do have Gimp, but guys how about some 'rectangular selection' tool?
7. Parental Controls: Vista has good parental control options. Currently in Ubuntu the only way parents can 'Hide' anything from their kids by using the '.' (dot) trick. To hide any folder you have to append a '.' before the file name, as in '.Home'. Although it does have one advantage that, 'kids' won't be able to hide anything from their parents.
8. Quick Shutdown: On my PC Vista takes around 4 sec to shut down, where as Ubuntu takes around 1 minute. The situation is expected to change in Jaunty Jackalope.
9. Media Center: Now a days (OK, change that to since past few years) PCs are becoming the new Entertainment center of our life. Vista has Media Center, which is head and shoulders above anything like it. Ubuntu should come with such software.

Even names like Sexy Scarlett (Johansson), Perky Paris, Arousing Alba would do wonders!
My favorite among these would be Kute Kiera (Knightly) and Kracking Kate (Winslet).
11. Speech Recognition: Vista's speech recognition is very cool. I wonder whether it can be replicated in Open source.