I really like the n810. There's so much that I like that I think I'd be better to talk about the things I੍ don't like. The list post will be shorter and easier to read that way.

1. Software installs/uninstalls are slooooooow. Is this reflashing itself or something?
2. Software installs/uninstalls don't automatically resolve dependencies. Sure they check dependencies and tell you when there's something you don't have, but it doesn't try to resolve and install those dependencies for you like the aptitude does on debian/ubuntu. I really expected the installer to be like that.
3. System updates have to be done with a computer. Really, why can't the updates occur over wifi like software? Just download to the internal memory card and have it reflash itself. I don't see what's so hard about this. Maybe I'm being naive, but I used to work on embedded hardware at IBM. Flashing SES firmware was always simple once you got the binary copied. It flashed itself.
4. Why does the default software suck so much? Come on. Nokia can do better than this. The media player should already use mplayer. Why should I have to go and download it myself? Again, probably being naive, but licensing shouldn't be that difficult if they would base it entirely on OSS instead of being half-in/half-out
5. Settings are scattered. You can't get to every possible setting from the control panel. For example, there are different kinds of lock. Only one of these can you change from the control panel. I already forgot how to get to the others.
6. Hold button is inconvenient. When the keyboard is out, I can barely reach it. Even while it's in, it's difficult to move quickly.
7. Power button is inconvenient. I can barely push it. If I didn't use it so much, this wouldn't be a problem though. Normally, you don't want to hit the power button by accident. I use it so much though for switching to/from offline-mode, that it's become inconvenient. If there were an easier way to get to that, I suppose, I wouldn't care as much.

I really like it otherwise though. Best one I've ever seen. I especially like that it runs linux. I'm a linux developer and I can't wait to hack it.