Maybe if I sit in the sun. I spent about 6 hours at RJ's Motosports Park for SCORRA's family fun day last July and I didn't really even get bothered by it. Of course it's "hot", but it's certainly not a deal breaker. I wear it whenever i'm doing a dual sport ride and/or am going to go ride single track.
My buddy got one that zips up in the middle. I honestly can't believe they even make those, it's just not a big deal to zip on the side.