I love these lights - they're really compact, very light and having used them for a few weeks, I'm no longer worried about them slipping off as I was at the start. They seem really reliable.
My only slight quibble would be the price. I'd have liked to get the Blinder 4 lights for visibility, but the price seemed a step too far which is a shame. You do have to pay for good design though and being able to charge these easily in the office or in a friend's house via USB is a huge advantage.