I write in fits and spurts in a lot of different locations. I started writing as a way to better use my commute time on the train. As long as I can get a seat on the upper deck, I'm good. There's a golden ratio of arm space to lap space to be had and there's less of a chance of fighting body odor in addition to writers block up here.
Lately I've been using a laptop, but I've been known to use my Gen 1 iPad and Bluetooth keyboard too.
May have to raise my book prices to keep up with the fare increases though.