Besides the fact that people don't make gains from them, they are very dangerous. Use often results in reptured blood vessels, and nerve/tissue damage. I highly recommend that you stay away from them.

First off thank you for you quick reply. Would someone still have the danger of reptured blood vessels, and nerve/tissue damage if they use a pump carefully w/ a guage?

Most likely yes, because the effects don't come from over pumping, but rather from continued use...