Anyone ever use/try a marine epoxy called West Systems?

Yep. It's all I have used so far. As Slipknot said it might be pricey, but mine is always leftovers from jobs, so not so pricey for me.

How's it hold up?

It's held up real well on the houses and boats:jump:
Seriously, west system needs to be covered from UV or it will break down over time, how long? I dunno. It has a super hard finish. I keep them hidden in my plug bag to protect from too much sun:btu:Between swims that is...