I don't know about the 800, but my experience with the 750 was quite bad. The reception and quality of sound from the phone are quite poor compared to the 700 from which I upgraded. Unless you have 100% reception, then the sound starts to fall apart quite badly - I never had this problem with the 700.
Images from the 2mp camera in the 750 are poor at best with severe banding and noise.
I don't know the 800 at all, biut I strongly recommend you stay away from the 750.