Well, I'm typing this on my Nexus One that just arrived. I don't have my SIM yet, but most everything besides the phone itself seems to be working fine regardless. Google Voice won't start without a SIM, either. There might be a way around that.

The trackball is actually pretty useful for cursoring back to correct mistakes in text entry, which generally works pretty well. One thing I didn't realize is that you don't have to tap the suggested word to accept it; if it's the default suggestion, you can just press the spacebar. And it does the one nice thing that my Blackberry does, which is insert a period and turn on caps for the next letter when you press the spacebar twice. In reality, I'm already typing much faster on this than I ever could on my Blackberry.

So far, the biggest problems I have are that if I go too fast, it will miss keystrokes, there's not apparently any shortcut to switch to caps, and entering commas requires a long-press of the punctuation button.