I have had a Nokia N90 for just under two weeks. I am going to say that I don't like the phone. It is too big and bulky for a modern cell phone. The camera is no better than other smaller phones on the market. The Carl Zeiss lens is a bit of an advertising gimic at the moment and the auto-focus doesn't seem to work very well. In fact, for the first few days the auto focus just wouldn't work. It must have been me though, because it did get working later.
See comparative pictures from my 6680 and the N90 here....
Another draw back is that the phone is not a 3G phone. Data is slow, which is not clever as the pictures are huge!!! As the world moves forward, the new multimedia phones MUST be 3G or better, otherwise people just won't buy them.
All in all, if you want a camera, buy a camera, if you want a phone with a camera, you are willing to accept that the quality isn't going to be great, so get a small one. Let's hope that the next generations of N Series phones from Nokia get smaller and cooler than the N90.