I use a J&G rain cape, and it keeps me pretty dry with far less sweating than a rain jacket and pants. You do get buffeted by the wind, however. How far, and how exposed to wind, is your commute?
It is pretty good but not perfect. The fairly long elastic thumb loops mean there is too much flapping of the leading hem, and it doesn't keep my gloves dry. Other wise it is very good and long enough over the butt
Remember to tie the waste ties. One time I didn't and it blew upwards all around my head like an inverted cone. Scary.