[Good, but inexpensive scopes?]

I would highly recommend Vortex if you can swing it for what you are looking for. I've got Nikon, Leupold, Bushnell, Sightron, and Vortex scopes on various guns. You really can't beat the value for the money on Vortex products. I have used Swarvoski and NightForce scopes on friends guns. Are they better than a Vortex? Yea, but marginally, and no where near worth it in my opinion. I have a Strike Eagle on my AR and love it, the 1-6 Strike Eagle is around $300, my dad runs the 1-8 Strike Eagle and he really likes that version, but it is pricier. Depending on what you do with your gun that you need the optic to be tough (traversing the woods, hunting, run-n-gun) I prefer the lack of a large objective lens, like on the Strike Eagle, if you are doing a lot of early morning or late evening hunts you may need a larger objective lens.

[How many failures are "normal"]

I run at least 200 rounds through a gun before I consider it fit for carry, and I want the last 100 rounds to function flawlessly. I will keep shooting until I get a solid 100 rounds down range with no failures. I actually prefer 500 dirty rounds, I feel like that round count really helps smooth out all of the internals and does a sort of de-burr job. I don't know that I wan't to pay for 500 rounds of .380, so I would probably just shoot until I got 100 rounds straight with no failures.