I currently have an HD2, my N900 should arrive in about 3 days, so I can post a comparison here.

RE: 65K colour limitation, in practice it just doesn't matter that much honestly. Mobile-review still rated this the best mobile screen ever - overall I agree (considering touch input, size, resolution, display technology). My i8910s AMOLED screen is just gorgeous, but the extra resolution and size on offer here really outweigh the AMOLEDs superior display characteristics.