Here's my list of little niggles. These are what I'd consider feasible for the next OS interation:-
Email
why can't I create events from emails?
How do I create labels from my phone?
Reply buttons at the bottom of the email - why not the screen (saving me scrolling through emails with massive threads/footers)?
Can I change the text size, please?
Calendar
I'd like to choose default view in Calendar
Great that my calendar colours are synced - nice touch!
Any plans for Task integration?
Contacts
Search only seems to look in name field (eg. not company)
Groups would help
Can I change the text size, please? Editing contacts with such massive text is very cluttered, with half the screen filled with keyboard too
Overall usability
While all text is very legible, control over text sizes on some screens would prevent clutter in some cases.
Need quicker/easier access to sound settings - eg. like profiles on Blackberries
Need quicker/easier access to time settings - why not long tap on status bar clock to get quick access to timezone/alarm/stopwatch features?
Maybe both above could be included as buttons at the bottom of the Notifications screen.
Power bar is great but needs phone power too (ie. toggle ALL network connectivity)
I LOVE the mini-screens on the homescreen when you long tap next to the menu button
Trackball as camera button - genius, although not obvious.