I had one and think it's a good light at a great price. I ended up buying a 6P LED to replace it (for $85) and kind of regretted it for a while. I paid twice as much for a light that isn't twice as useful. Of course, the 6p is a great light, don't get me wrong....
Back to the XO. The things I wasn't thrilled about were the lack of knurling and the switch. I now own a T2 and think it nails everything the XO missed, It's got a great momentary/clicky tailcap and very nice knurling. I got a deal on mine and paid about the same as an XO would have cost.
Do LOTS of reading here before buying. By the way, Target has a 90 day money back guarantee.