Does setting the Computer Sleep setting to 'Never' prevent sleep? I'm running OS X 10.8 Mountain Lion on several servers. We're about to ship them off to a colo provider, and I wanted to prevent them from sleeping.

My question is, does setting the System Preferences > Energy Saver > Computer Sleep option to 'Never' reliably prevent sleep?

I noticed yesterday that all the mac minis were off, despite the 'Never' option being set. However, I'm thinking their power strip may have just been accidentally unplugged for a second.
Yes. This setting reliably prevents a Mac from sleeping. I've had my iMac set to "Never" sleep for over a year, and it's still running (though its display turns off after 10 minutes or so per the other setting on that screen).