First impression - I would better buy N800...

N800 vs N810
+ Larger screen vs - Smaller screen
+ 2 SD cards (cheaper) = up to 64GB vs - 1 mini-SD and slow internal = up to 34 GB
+ mini-USB vs - micro-USB (damn expensive and hard to find)
+ price about $410 vs $670 in my country...
+ screen keyboard can be accessed with hard joy simultaneously vs - if you touch screen, then you can't move cursor by arrows...

keyboard can be external BT for N800
GPS can be external BT for N800 (even internal N810 GPS is useless in my country)
OS2008 саn be installed to N800
size or weight doesn't matter - I care device in large case or bag

just only two preferences I found - USB OTG in N810 and good reflective screen

I think now I was wrong buying N810... but may be later I will think different, don't know yet