Well, camera on phone these days is so good. Sometimes you just can't distinguish whether photo is from camera or just a phone. Nokia is well-known of impressive camera on phone for ages N900 is no exception. N900 camera focal length, according to EXIF data, is 5mm which is equal to 35mm on film roughly which is about the same as one on Nexus One also. For the quality, take a look by yourself.
left: taken by N900; right: taken by Nexus One
All photos are taken by default program and setting.