I'm currently running a 2011 Mac Mini Server as my recording rig. I run
Logic Pro 9 and it runs fantastic! I record pretty much all instrumental Rock stuff - drums are programmed using Logic's Piano Roll Midi Editor and procressed with Steven Slate Drums v. 3 (which uses the Kontakt player - pretty resource intensive). Most guitars and bass are run through
Amplitube 3 on it's hi res setting, which is also pretty resource intensive - then into MixIR - which is a means by which to add speaker cabinet/mic emulations to my modeled amp tones. Then quite a few plugins. There are always quite a few guitar tracks so all these plugins add up. Then Drums, Rhythm Guitars and Lead Guitars are all sent to their own respective sub mixes, Aux's are set up with various plugins, etc.....
The Mac Mini handles it all beautifully! With all of those guitar tracks running through
Amplitube then Speaker Cab impulse responses, occasionally I'll get an overload error. This is easy to get around though, Logis allows you to 'freeze' individual tracks, which basically does a temporary mix of each track selected with all the plugins applied. This way on playback it's just playing back a static audio track, much less processing overhead that way. Then if I need to edit audio or plugin settings on one of those tracks I can simply click off the freeze button, work on it, then click the freeze button again to refreeze it.
When I was researching whether going this route would work, I hear quite a few people referring to the Mac Mini Server as Apple's best kept secret. After using it for over a year I'm inclined to agree. Potent little machines...
The only reserve I have is that from what I understand, the current MMS comes with 5400rpm drives. That's not a good thing. But from what I've read, the hard drive in a Mac Mini is pretty simple to replace. I haven't done it but installing RAM IS simple and quick. Word of advice, order your RAM elsewhere, Apple charges way too much to upgrade it. I think the newer Minis hold up to 16gb of RAM (mine, being older, maxes out at 8 gigs but it runs great on 8 gigs). You can search around online and find that for a Mac Mini for a little over $100 (may be less, I paid $39 on amazon for 8 gigs of Mac Mini RAM in January 2012). And like I said, it's dead simple to install.
So I say go for it, you won't regret it, even if you do need to replace the drives with 7200rpm (HIGHLY recommended) or even solid state drives, but they're much more expensive.
Enjoy!