Ok...
7(?) The GPS in the N810 varies between sucky and downright useless, and the general consensus is that you are better off with a £20 bluetooth one off amazon or something. I use one with my N800, and it's brilliant. It depends on the mapping program as to storage - maemomapper requires you to either download on the go or download the maps for where you want to be before you get there (they are large as they are based off google maps etc) and you need to download routes, but the built in mapping program downloads full maps and shows you where you are, though you have to have a license for route planning.
8) Emulators? If you mean gameboy etc, I use the gameboy pocket one and it hasn't crashed on me once. Seriously. I thought it did, but it turned out I was mashing the back button by accident when I got to an exciting bit in Mario, which is the quit button. Garnet, the Palm emulator, has some mixed reviews - it's good for some things but not all.
9) Community seems good, but that's not really for me to judge. Chances are high that Fremantle (next Maemo) will run on N800/N810s in some form (both units share the same internals, with the N800 having 2x full size SD slots and the N810 having a keyboard and 1 micro-sd slot. You can quite happily run full distros on it. I run emulated debian on mine (called Turbo-Easy-Debian) and can happily use Openoffice and the Gimp if I have to. Android is also rapidly maturing on the device.
10) Wardriving works after a fashion - you can passively break WEP, but no active injection attacks. You need some linux system familiarity for this one, because it requires the command line. Try looking up Kismet and aircrack-ng.
10.5) Wifi strength is a major plus on my N800 - it's better than my laptop.
11) No idea, UK. You can however download the Maemo SDK (scratchbox) and run it in there on your PC (linux required methinks).

Video support is brilliant once Mplayer in install, playing probably any codec you can think of and then some. I use Knots, which allows me to stream videos to the N800 over my network from a media PC downstairs, and it works brilliantly - I can even watch Blackadder DVD isos.
This thing is effectively a small form-factor netbook without a proper keyboard. A bluetooth or USB keyboard (and a bit of squinting) and it's perfectly usable for 99% of tasks. It's unfair to compare it to the ipod, which is an embedded device designed to do a few tasks and do them well. It's in a different league in terms of functionality.
I would however consider getting an N800 instead of N810. You can use the money saved to get a keyboard and bluetooth GPS (which you'll probably need anyway) and you can expand the storage space to 32GB (2x SD cards).

Hope this helps, I've had mine since christmas and couldn't do without it, was considering a netbook but went for this instead for £100. Haven't wanted a netbook since.
(I have fairly good experience with Iphones/touchs and they are good but only for the limited number of tasks they are designed for. I'm also fairly linux experienced - if you get an N8~ it helps when doing some of the seriously advanced stuff this thing was never designed for (wardriving, running web servers, repeatedly rebooting housemate's Ipod touch via SSH), but is by no means a requirement. It's just there if you want it).