Yes I believe so. You can double-check with Skype support, but I just checked, the SkypeIn makes no mention of outgoing calls... the same is true, but in an opposite sense, with SkypeOut.
Good luck! I believe Skype will even refund your money if you're not happy (might want to double-check that), so it shouldn't be a huge risk to just try it out.
And the N800 is definitely a nice little device! Congrats in advance if you buy it

I hope they start bringing UMA here - I'm not sure if you've heard of it, but its basically where a cell phone can, in the presence of hotspots or your own WiFi network, route calls via VoIP (using yours or other trusted WiFi networks) instead of the cellular network, all using your same phone number with the transition being so seamless to the point where one can switch between cellular and UMA networks without dropping calls or interrupting them.
Not only would this mean GREAT news to people who might not get a great signal inside their homes, but also reduces congestion on the cellular networks (especially on chronically overloaded networks like Cingular), and possibly lower per-minute rates while you are at home.
I think T-Mobile (who is who I use now, left Cingular a few months back) was going to do it - but something happened, and they didn't go through with it
