Wahoonc is right, IMO, the main advantage of the rain cape would be airflow -- in warm weather, you sweat in raingear, period -- claims of "breathability" notwithstanding.

That said, I use the O2 Cycling Series rain jacket and pants (along with Burley shoe covers), and they are very nice (and inexpensive!), see my reviews here: http://kentuckybicycling.com/category/review/