Must admit the IQ Premium does look good, best price I can find is a touch under £50. One thing I can't grasp is why can't any bike company manage to make the bracket as good as the light. Virtually every one you look at says the brackets are naff.
I don't think it is so much that the brackets are naff rather than the lights themselves being heavy.
Most lights that are actually powerful enough to see with (rather than be seen) and have decent battery life are usually quite heavy - often having 4AAs on board or a big rechargeable battery.
Sheer inertia means that hitting a bumps or potholes can result in the bracket moving around on the bars, which can result in everything suddenly going dark - not good! If you manage to get the bracket tight enough not to do this, it then becomes difficult/impossible to adjust the aim of the light on the move, which can be very handy.
I had exactly this problem with a Philips Saferide. It weighed a ton and I spent more time trying to point the thing in the right direction than looking where I was going - completely useless and only really fit for the bin. This was an expensive light at the time too, recommended by the 'you get what you pay for' merchants due to it's German style optics. It also had rubbish battery life, was unreliable and at 80 lux, not exactly bright.
If your light doesn't weigh much, you can have the best of both worlds. It isn't as affected by bumps and can be fairly loosely mounted for quick on the fly adjustments.
The correct solution to the problem is to decouple the weight of the battery from the lamp - just like the Chinese do with their excellent quality yet reasonably priced lights.