If it's cool enough and I ride slow enough I won't sweat that much, but I don't like riding slow.

Neither of my first two cars had A/C. The second one had vinyl bucket seats. Sitting in stop and go traffic for an hour on a hot morning meant a pretty sweaty back. The only reason I mention that is to remind people that sweat is part of life whether you are on a bike or not. If you never sweat, you're doing something wrong.