Does anyone have a good or bad experience using a PC server rack for audio equipment?

Thanks for the feedback.  It definitely will be more secure than what I have right now.

If vibration becomes an issue, you can always add something like the IsoAcoustics Gaia's to support the entire rack. Most racks come with threaded feet, so it is just a matter of replacing them with the weight-appropriate Gaia's. If the threads don't match IsoAcoustics is very accommodating and have a wide variety of threads available. If the rack's legs don't cooperate then you can always follow @mikhailark suggestion of building a platform.

That's a good idea, I am also thinking about some 4" rubber wheels, makes getting at the back of the equipment easier and also provides some portability.  Those are not major ticket items, just makes things more convenient.       

Frankly, a PC server rack might be the worst solution for audio gear.

It rings, there's no vibration control for sensitive equipment, and it's only designed to keep a bunch of boxes in place that come with their own built-in vibration control if needed.

No footers etc. in the world would make much of a difference, it'd be lipstick on a pig.