In reply to AJK87:
I have an slightly older Hydrogen Extreme Smock and the new Kinesis. I got the Kinesis for just the reason you mentioned, the Hydrogen was a bit too warm for me. Even with all the zips open I sweated too much for comfort on approaches. I also found the arms to be a little short, but I have freakishly long arms, so that is mostly my fault.
The Kinesis fleece feels thinner and isn’t quite as lofty as the Alpha Direct. For my purposes it is a little nice, not as sweaty. The arms are a little longer and fit me a bit better. The torso is also a little longer.
Little details:
The cuffs of the Hydrogen are a little bigger and fit over gloves a bit better, but the Kinesis cuff Velcro does’t flap as much.
Both hoods fit well over and under helmets. The Hydrogen hood gives slightly better protection.
Over all I rate the Kinesis slightly better as the fit works better for me and it’s warmth is better suited to how warm I tend to run. I would be really happy if it was offered in a smock.
I would suggest the Hydrogen for people who run colder and don’t have freakishly long arms.
hope that helps.