Ok ive had the N80 since first day release, got it sim free but it got sent back after a few days of playing with it.
Anyways its a nice phone, no doubt about it but the build quality leaves a lot to be desired for imho. The slider mechanism is ok but is going to get loose in time, not only that its a bit of a brick but then the w900 isnt a small phone either.
Other than that the screen on the n80 is nice, is it as nice as the w900??, well my mate has the w900 and i found it to be a very nice phone..bit big and chunky but i quite liked it tbh.
The n80 i had was slow and cumbersome imho, it also had a big problem with memory leakage and usage...just opening the web browser caused the phone ot crash and crash big time ie had to physically take the battery out in order to get it up and running again. It is a smartphone no doubt about it but imho not a very good one, has some great features but i found it extremely niggly compared to other nokia smartphones i have owned in the past.
My honest opinion of the n80 is that it has some great features, all the features i could have possibly wanted in a phone including built in wifi but the way they implemented it was terrible imho. I ended up getting the SE W810i which im much more happier with even though it hasnt got as many features as the n80 but im waiting for the p990i to be released as SE know how to make a great smartphone...look at the previous p series phones...all raved about.
Like i said this is all my opinion, really at the end of the day you need to choose a phone which suits you...would have been nice if the n80 wasnt so niggly as i would have kept it.
The camera on the n80 isnt that great tbh, my w810i takes better sharper pics than the 3mp camera on the n80 and the 810i only has a 2mp camera. Thats one thing i wasnt too impressed with the n80...although one very very cool feature is instead of using a ringtone, you could have the phone actually say the callers name

...quirky feature but tres cool at the same time
