I think the physical size of the 800 is pretty much perfect, and I prefer it over the larger 900, but the 800 has a few feature shortcomings that make me hesitant.
I definitely find the lack of a forward facing camera on the 800 to be strange. The 710 has one, the 900 has one, but it's missing on the 800 ?
Last time I bought Nokia (my current phone) was a long time ago, because the thing has proven to be almost indestructable. I was hesitant then about a few missing features, but went ahead. No sooner did I, and Nokia released an incremental update that addressed every one of my concerns... Doh!
Perhaps Nokia already have an 800i planned.