Ever use a Joe Rocket.

Very nice.
The fit under the jacket is nice.
Granted I wore it under my leather and not the Ballistic it was meant to go under(Will test that in a few minutes).

I am happy with it.
It kept me warm on this mornings ride to school.
Albeit was still 55-60 out.

It is made from INTERON (breathable/H2O proof/ Windproof)

Retails at LBS for $30 bucks.

I paid $25 for mine through New Enough and am quite happy with it. It's great for cold mornings/warm afternoons in that you can unzip it from your jacket and, with just a little effort, stow it below the rear seat for the ride home after work. Plus it's waterproof and is a nice way to keep dry if a sudden squall breaks out.

I just did the test with the Ballistic jacket.
A little cooler than with the leather, I know that is obivous but I thought I would say it anyway.
All-in-All, its pretty sweet, now for the rain test!