I do, because I don't want to spend money on another smartphone and have to learn to deal with a whole new set of issues. I've even considered going back to a dumbphone just to get that great reliability back...Meanwhile I am trying to use the N900 as best I can. Right now, if only if would:

- reliably send, receive and display SMS and IM (without e.g. messages being stuck and not sent)

- show the lock screen every time I push the power button

- not get stuck with the blurred screen when I'm about to make a phone call

I've recently used it to good effect (if with an unhappy ending), see here http://talk.maemo.org/showthread.php?t=88756