The only negatives I've found with this light are the clear plastic window over the led indicator light and the plastic latch used to hold the case shut.
Arguably I've abused my light and it's been used as a torch for a fair bit over the winter whilst shovelling snow and ice in the dark, which meant, inevitably, dropping the damn thing a few times.
I lost the plastic cover somewhere in a load of snow in the dark so have just taped over the hole to keep in water proof (I don't need the led indicator, I can tell what setting I've got it on).
And also, probably related to the number of drops it has had, the plastic latch that keeps the battery compartment shut broke off. This is much more annoying as it now means I have to tape the light shut every day until I can figure out if I can mend it (since I need to take the batteries out to charge them - a good argument for getting the charger you can plug straight into the light). The casing is also slightly sprung so keeping it tightly closed is tricky and if the casing opens slight the batteries can come out of contact resulting in no light (Aaargh!).
It is still a good light. And the drops and impacts haven't stopped the light itself from working and I still struggle to tell whether a car is coming up behind me, or whether it is just my light ;-).