It's really too bad about the Mars 3.0, because I like the concept of that light, but the execution just sucked.

I never experienced the cracked mount (I had two of them) but they would occasionally slip completely free over a bump and clatter to the ground.

The screws (an incredibly annoying idea, btw) corrode badly, so I'd recommend greasing them. But even so, you'll have to guard against stripping the threads of the light. It's a fine line between getting them tight enough to seal, and tight enough to wreck the damn thing.

Both of mine ate batteries to an alarming degree, such that I rarely finished a day of commuting (1 hr each way) without discovering that my bright rear flasher had turned into a dim rear glimmer.

[oh, and because I was changing the batteries so often, the screw heads started to get rounded off. At the end of my Mars 3.0 experiment, I had at least one screw that I would have had to replace had I not simply chosen to pitch the whole thing instead]

I replaced them with Superflashes. Long battery life, super bright and if I lost the side visibility, I've made up for it some by using three of them with one on the left chainstay pointed off axis (and slightly up) towards traffic.