I dont think they changed the screen. I think it is just the same hardware with some new cosmetic features. No-more side talkin, or taking the back off to change games as well.
The n-gage in principle is a good idea. Unfortunately, Nokia's implementation of it was particularly fraught with problems, imo. A few simple chnages and it could be actually a good system...

- discard side-talking (I believe this has been done in the next version)
- move MMC slot to not behind the battery (likewise this)
- rotate screen 90 degrees, and preferably increase its size
- release an SDK to get yourself a potential underground scene

Those 4 (ok, 5 for the resolution increase) things would have made the ngage a great console, I believe. Without them, it falls squarely into mediocre...