In reply to lanky:
I think the alien ones I have are the alien classics, as I bought them after the original, original aliens had stopped being made. But I'm not 100% sure (they look identical to google photos of the classic though).
I have 2 blacks, 2 blues and a green. They are pretty great pieces of kit, getting into really tiny, crap placements. I have used the blacks and blues quite a lot but I don't think I've ever fallen on them. The green one broke when one of the ferrules at the end of the axle came loose and fell off and that means the lobes can just full of the axel, so it's toast. The blue and black ones are still going strong. If I had to identify an irritation, it would be that the trigger wires bend from their manufactured shape to more or less straight after you've pulled the trigger back firmly a few times, which means when the trigger is released, the lobes go past the intended start position and invert somewhat (there being no camstops), it doesn't make the cam any less safe, just looks a bit strange and means you must be sure to pull the trigger at least far enough to get the lobes back past their fully open position before you ram it in the crack (otherwise, if you just ram it in without pulling the trigger, the placement could be with all the lobes inverted, which won't do jack when you fall on it).
Edit: Worth looking at the ranges too. The alien classics have a fair bit better range on each cam than the dragonflys, for example. (Though I couldn't find range data on all the cams LucaC spoke about and I'm too lazy to spend more time looking!)
Post edited at 12:26