It's always been one of my more favorite objects, certainly my favorite kryptonite. There was actually one match that was won in last weeks tournament, with a great deal of the victory being owed to the X-Kryptonite. I was using a soldier team including Dirk Anger, Faramir, and rookie Domino... The positioning advantage it gave me for these stealthy characters, particularly for Dirk Anger, went a long way to making sure they were always in the right place at the right time. So I would say if you like cheap stealthy grounded figures, X-Kryptonite should be your go to object of choice.
Forum Team Building Contest #2 and #3 Winner, & runner up for #1 and #4.