Has anyone ever tried to fire any previously de-capped but still live primers? Did they still fire reliably?

Simple answer - yes they do !
As long as you've deprimed gently...

Kirby.

Yep - as Kirby says, go easy on the decapping process, drop into a clean reciptacle and reseat. Nary a misfire in all that I've reused.

Ditto to the above. I'll add a caution that these primers should be used for plinking or target practice. They may not be as reliable as normal, which could prove fatal if your life depended on the ammunition, or fatal to your score in a target shooting competition. A crack priming compound may result in burning that is a little more irregular than normal in flame production. That just means, it may not be consistent enough for benchrest competitors. Not much is.

Because I'm sorta cheap,I use all decapped primers for fouling shots or plinking.
I'm careful when decapping and never had a misfire or hangfire.
Know nothing about any accuracy degradation,though.
Frank

Ditto what unclenick said. Been there, done that:)

Use then all the time-regular loads! De-cap rounds to fix brass! Reload shoot as normal!!

Hey, cool! Thanks guys. I de-capped a few yesterday. Sad part is, I don't have dies for those anymore so I used the manual method and tools (i.e. caliber-specific decapping rod and a hammer). I took significant precaution against them going off and shooting the decapping rod up and sparks/flames around, and it worked fine.

I'm thinking that I can use these for .30-30 plinkers. Thanks again!