I think the main factors of growing anything up here is going to be the lack of daylight hours in the winter (on some days in December the sun rise wasn't until about 9.15 am and sunset was at 3.15pm!), and the wind.
Having said that we've had a fairly settled winter so far (famous last words!), but even the positioning of polytunnels is going to take some serious planning, and also the type of tunnel. The thin plastic varieties wouldn't last a day up here.
I can't wait to start, and it's going to be really interesting to see what happens, and what does and doesn't grow. I'm quite glad that I'm reasonably experienced in growing my own veggies though, think it would be rather daunting if I was a newbie starting out up here.