Touch screen is sensitive although Nexus-S may have a little better sensitivity - while typing on screen I had a couple of errors, definitely more than Nexus-S but it may be counted to slightly different virtual KBD size and layout.
However, both buttons - UP/DOWN and POWER are located on the same right size, in N900 style. Plus POWER button is bigger (regular size) and it is difficult to avoid pressing it while keep N9 in left hand. At least I accidentally switched N9 off once. I am surprised why Nokia didn't put it on any short side.
(no host USB ). The adjacent SIM slot is actually a hole with SIM card holder (regular SIM for development edition which I played, it should be microSIM in production).
No visible way to open a body but SIM card hole has an adjacent screw deep in hole. There is no even thin gap between screen and body.
Forward camera is in right down side. But I didn't noticed GTalk (may be lack of time or it is hidden in "messaging"), skype is a separate.
The downside is - it has only one home screen to place your widgets. In comparison with N900 all windows are sharp and you can see that is going on on any.
I should say that there is no Adobe flashplayer and (probably) - no Java (N9 is HTML5 based), so his result seems to be 50-50.
Multitouch works fine in browser and maps but browser wraps up only with some pages
Map was designed specifically for driving, at least Nokia people stated that. It seems fine in 2D and good enough in 3D. Positioning works with any GPS standard (A-GPS etc) and it may use "WiFi positioning" - I think it is a Google-like WiFi positioning. Maps for your continent are preloaded before device will be shipped to you and it can be used offline, w/out cell-phone coverage(!).
Also they said it has all 5 mobile world data frequencies and in fact only CDMA and Japan phone variants are missed.
Device has an embedded "development" setting - then I pressed it downloads 20+MB and Terminal apps occurs.