CON - even if things work now, they can and will break in the future (removed hardware support etc)
- every update takes time and work
- don't even think about running it on the hardware you already have - only use specifically built systems (such as those linked)
- backups aren't as nice as on a mac (disk cloning, time machine)
PRO - you get a lot of harddisks (internal, cheap and fast ones)
- it's almost stupid not to use a raid setup (such as 10)
- serious GPU power is affordable, but OSX is picky
- repairs are really really cheap