From the list above, I like
2. Cut/Copy/Paste
3. Built todo list in calendar with Google sync.
4. Improved application switcher that handles application switching better than holding down home button.
Would be nice but not all that important.
8. Built notes application with sync to Google docs.
I'd also like to see some UI improvements but not what most people are thinking. I want Android to mostly stay the way it is but, for example, add sharper buttons like what we've been seeing in a lot of the 2.2 apps. In general, change up the way the built in widgets (not home screen widgets) look or perhaps make it easier for developers to change them. This would essentially be the same things. The biggest improvement I'd like to see is a theme engine. HTC put one in the Slide and while I'm not crazy about it, the idea is there. Android should have a way for developers to create themes to change the entire UI of the system. This would create a lot of new apps and allow people to seriously customize their devices.
Most of all, the Market needs a ton of improvements. Without going into too much detail since it's been discussed many times elsewhere, there needs to be better searching/sorting methods, a way to browse AND purchase online, added payment methods and, most importantly, paid apps must be expanded to all countries where Android is available. And for devs, there absolutely MUST be a way for developers to respond to Market comments. Without this ability, comments are all but useless. As a dev, I've seen comments that are simply lies. Not accidental but malicious lies with no way to clarify the situation.