I have one but have never actually used it. I purchased it due to its ability to remove things (bugs and chemicals) other filters wont and because it has lots of adapters (nalgene, soda bottle, etc.). It's way too big and heavy to take backpacking so it sits in my emergency kit hoping to never get used.

I use my SteriPen for backpacking. Full review here:
http://adventurereports.blogspot.com/2011/06/steripen.html