Flimsy. The main points of failure are:
The electronics are unimpressive. It's nice that it's built around four AAA rechargeable batteries, but they packaged it with regular NiMH, not low-self-discharge NiMH batteries, so if you only need it sometimes, it won't be charged for you. I don't use the trickle charger that comes with it, because I've got a nice LaCrosse charger.
There's a "low battery" light that comes on almost too early.
It's quite inefficient. You get a few hours of usage out of four AAA batteries. My Cateye HL-EL320 light, which doesn't have anything near a 1W Luxeon, has both more power and significantly more battery life. I worked out battery life vs. lifetime and it looks like they are getting about 1W of power out of the battery but they are either using a very old and dim Luxeon or they are not driving it very efficiently.
Like most LED bike lights, it's got a hot spot in the center of the beam and then a fairly dim but wide circle of light. This makes it look good in the store but isn't as useful as you'd like.
This is an example of why Performance Bike sucks. By the features, it's great. But it's just not reliable because they cheaped out in various areas. Pretty much, a few days after you get it out of the box, it's going to start to tall apart. I replaced it once and eventually, gave it to a guy who had no lights. I don't recommend you purchase it, or any other Performance Bike branded or Bike Nashbar branded lights.