I find it's not that much warmer to ride with long sleeves, as long as there is a breeze or you're making your own breeze.

I have those cheapo Performance long sleeved jerseys in every color:
http://www.performancebike.com/shop/...tegory_ID=1211

and I wash them with this:
http://www.ritdye.com/sun_guard/default.asp

As a side note, I love the jerseys, they fit perfectly and they're a great weight. I only wear them for longer rides, over an hour or two-- I don't like being slimy from sunscreen and sweat -- or in the cool mornings instead of armskins.