Way cool. While I have used "Great Stuff" in the past, the only thing that ever bugged me was once you opened the spray can, if you didn't use the entire contents, it was difficult to impossible to use again. And I could only find it in the one size can at the local Home Depot. Haven't had a need in a few years though now, did they ever make available smaller size cans?
Being messy is typical of just about any foam and your should always wear some sort of gloves if you're going to be in direct contact with it. If you do get it on you let it set before you try to scrape it off otherwise you'll just make a bigger mess. That stuff's a real b1tch to get out of the hair on your arms. I ran machines that foamed refrigerator cabinets for around 2 1/2 years so I've had enough "fun" with that stuff to last a lifetime.