My only computer is a 17" laptop. (It's a Mac PowerBook, as it happens, but size differences between brands and models are small compared to the difference between anybody's 17" and anybody's 15".) I travel with it. More of my travel than I might wish is in the small seats.

I find it workable. It's difficult to juggle the laptop and a drink at the same time, so I generally get soft drinks in cans and put them next to me on the seat. (So far no accidents, but if I had one, my clothes and the seat would suffer less long-term damage than my laptop would have.) The issue is more screen height, seat pitch, and recline (yours and the seat in front) than width. It helps to be skinny, which I am. If my belly was much bigger, a large laptop in coach might not be workable.