i wear them year round except when it's really cold (just them...who the hell wears underwear under their short tights???), they fit great and are very lightweight & breathable. i wear 6in inseam ones as the 9in ones are way too long and almost cover my knees....you'll look like a chick headed to the gym to for yoga class if you go for the 9in.
another great lightweight short tight i'm wearing is ASICS Men's Core Lycra Running Short - slightly heavier and don't fit quite as snug, but usually 5-10 bucks cheaper than the pro combat gear.
http://www.runningwarehouse.com/descpageMRA-AMCLS.html