Well, you've pretty clearly stated the things you like & don't about it (and they look to be well-thought out and reasonable reasons as well, unlike some), so you're well aware of the pros and cons. If your specific requirements aren't being met currently, and you don't want to wait for software which may/may not be produced to meet them, then your best bet is to take the plunge and return it while you can.

If your current phone is meeting all of your current requirements, I'd suggest holding off replacing it for a little while. That'll give the Nexus One time to get past the "ooh, shiny" stage (and the inevitable issues will become recognised), the N900 to get another update (and new software to come out), and the iPhone 4 and WM7 to get past the "rumour" stage. That should give you a lot of options to choose from.