Yes, I got my Surefires second hand as well. Great deals on EBay. One lasted for years, and when it went finally went down (older model, lots of use an abuse), Surefire replaced it with the current upgraded model, no questions asked. Amazing customer service.
Streamlight is a good value, but not build as heavy duty (there are entire articles comparing them in detail), and most importantly more me, the toggle butterfly switch is uni-directional. Only one direction is used for constant on and other other for momentary. Personally, I find the complete ambi set up of Surefire a lot more user friendly, intuitive and better for stressful situations.
I borrowed my friend's Viridian and ran it for a couple days. While the green laser is super bright, the adjustments were horrible, build was very flimsy, and I seriously doubt it would survive one accidental or intentional knock against a barricade or drop on the deck. I would definitely hesitate to bet my life on it
my $0.02