Has anyone used one of these:

http://www.amazon.com/dp/B0018Z02T0/?tag=cakecentral-20

it looks like it could be a good thing, but wondered if anyone had any experience with it.

Thanks.

I have seen these, but never in person or in use. I would want to know what thickness of line the pen produces. The picture makes it look like it would be fairly thick. Okay for on larger things, but not so good with detail work.