only to load an emulator on it
Ahem, in typical free software's time-honoured recursive acronym tradition,
Wine Is Not an Emulator 
to run windoze XP so they can run the software they actually need
I do not run any Windows applications either (let alone a Windows OS).
OTOH, running Windows in a virtualised environment would still count as running Windows, not *nix. I have never tried it but I imagine that could be a good way of ensuring a stable Windows platform for kiosk-like use, by reverting to a known-good (and safe) configuration on every reboot. I think I might be digressing a bit though
In any event, my computing platforms cover my flight planning needs very well indeed.
Getting sidetracked for a minute again, I also note that a Linux system would be ideal to develop specialised solutions such as, err... inflight connectivity
I'm thinking about things like the relative ease of programming cheapest-path connectivity, opportunistic caching for latter use while on a cheap link, etc.
But to get back to the topic, yes, anything with Wifi+GPRS, a screen readable enough to read SIGMETs and NOTAMs, and a web browser to fill flight plans and book accommodation, etc., is about all you need. A flight planning application is a nice extra.