Some people have a hard time getting used to them.
I like them, especially in low light.
As for durability, I can only say, you get what you pay for.
I wouldn't buy the $29.95 set.
Check out Dawsons. I've used them with good success, really helps aging eyes.
I find fiber optic works great when you're on a range in the right lighting conditions, but falls apart indoors or in low light. I have yet to break one, but I've never bought a tiny tube fiber optic sight before.
In all honesty, testors florescent orange paint works equally well for me. It can just be tricky to get a good buildup and application that won't wipe off.