I have a few accessories from Serfas: a bike helmet, a couple of front lights, and a tail light. Here's the short of it: The products look nice, but they're all cheap junk and I'll never buy another Serfas product again.
Here's the longer detailed version.
Helmet: It's a nice looking, comfortable, well fitting helmet. I especially like the knob on the back by which the helmet is adjusted. Unfortunately, the knob fell off and the adjusting strap is free to slide around. This helmet is a $50 piece of styrofoam junk, now.
Front light: I have the Serfas WhiteLED front light on one of my bikes and my son has one on his bike. I really like the fast flash mode and the five LEDs seems to work well to get the attention of motorists in front of me. It's small and unobtrusive on the handlebar and, frankly, I think it's the nicest looking light out there. Unfortunately, these lights are also cheap junk. My son's light has never really worked properly -- it has a tendency to just switch off spontaneously for no apparent reason. Hitting any reasonable bumps results in the cover popping off and spitting out the AAA batteries.
Rear light: I have the Serfas RedLED attached to a seatstay of my fixed gear bike. Like the other Serfas products I have, it looks sexy. The lack of a prism lens is a minor shortcoming, and the light is significantly less bright than any other rear LED light I own. No matter how much I tighten the bracket screw, the light won't stay in position -- it continually droops down so the light is pointing at the ground instead of toward the rear. It also has the spontaneous turn-off problem that my son's front light has. On a positive note, I've never lost any batteries with this light.
I also own Vistalight and Cateye lights. They're ugly but they've been rock-solid dependable for me.
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I've seen comments regarding the quality of Serfas lights. But I went ahead and tried both their handlebar tape and some tires - Seca blackwalls in 700x28 - and they seem to be decent quality. I've had the tires for about 6 months. Most tires last a year or so on my commuter because the UV light eats them long before they wear out. I'll let you know how long these last. They're not as stiff and my Continental Top Tourings, but then again, they cost much, much less.
I've returned two Serfas SHL-01 lights for free replacements, but unfortunately the new ones shut off just like the old ones. I stretched the springs that connect to the battery holder about 1/8 inch and the problem seems to be mitigated. If the lights shut off again I'll replace the springs with soldered wires.