i have two. A really old paragon kiln that I use as a back up for when I get really busy, and my main kiln is a Paragon SC3. I love it- it really can't be stated enough how much I use it and love it. If you are interested in base metal clays or sterling clay, a kiln is really the way to go.
As far as negatives- they only down side to base metal clay firings in that it oxidizes the steel pan and that flakes off. But they use so little space, not a lot of power, are very versatile (I also enamel in mine).