In reply to Gadameer:
Ruigh Aiteachain is relatively low, below the snow line, so you'll be booting in and out.
I stayed at the Hutchison the other weekend, v nice ski in ski out typa thing. (bring a bag of coal for the stove, get your mates to carry it)
You can cycle up from Braemar to Derry Lodge but I don't know if you can get anywhere up Glen Derry before you have to walk (we skined over from the gorm car park)
I'd keep a eye on the wind direction; windward slopes will be boilerplate ice and not much fun to ski.......