Can't speak for your users, but there are at least 2 UK based companies who sell boxen with Linux pre-installed, both have been around for 5 plus years, so there must be a market.
I'm not at all careful of where I go on the Web -- and I run a P2P client pretty much 24/7 (there's so much interesting stuff out there). I suspect my mate has particular problems with his Windows install because (apart from running without AV unless I insist on putting one on) he's forever grabbing music files from the Net (rather than P2P) and insists on using Chrome or IE.
My biggest issue at the moment is with this site, which often locks up Iceweasel (Debian build of Firefox).