I've been using the regular TLR-1 and it's been great. Very bright beam with the C4 LED, super tough, great rocker switch, and it stays put with the assorted keys that fit particular pistol rails. I haven't had any problems with it yet, aside from having to clean the lens of powder residue.
I do like the Surefire, but the cost is way too prohibitive for basically the same thing. You can find the TLR-1 on the web for under $90, whereas, the Surefire X300 is well over $200.