2012 Motobecane Fantom CXX, 2012 Motobecane Fantom CX, 1997 Bianchi Nyala, 200? Burley Rock 'n Roll
I have the Serfas True 500. I've only had it for several weeks, but I think it's a great light. I like the amount of beam spread, evenness, and light color. Personally, I think the upgrade from 250 lumens to 400 - 500 range is well worth it for my commute (although I commuted for a few years with a 200-ish lumen halogen light). I ride in city traffic on lighted streets at speeds generally 17 mph or less.
The light seems solid and well-made. I think it uses the same mount as the 250. The mount holds the light very securely, and I've had no issues with the mount rotating on the handlebars. It is very easy to adjust the mount to fit different diameter handlebars. Extra mounts at the Serfas site are far less than competing brands, which is something to consider if you want multiple mounts to leave on different bikes. It gets moderately warm if you run it at room temperature on the highest setting with no motion (but the only time I ran it that way was inside to test the runtime). In normal use it gets very slightly warm.