Are there any potential (or known!) issues with running more than one client at one time? I'm running my Bitcoin client full-time at the moment but I also intermittently run clients for Feathercoin, Namecoin, and others from time to time. I was about to fire up my Feathercoin client but suddenly wondered if I should shut down Bitcoin-Qt first? I'm running OS X Mountain Lion
I haven't had any issues with multiple clients in combination with Bitcoin-QT.
However, some of the Scrypt coin wallets seem to give my mining PC an unexpected Windows Blue Screen at random times, and not sure which wallet it actually is.
It's neither Feathercoin or Namecoin though
Not sure if this makes any difference on OS X but if it's not on your regular pc, you might want to keep an eye out for lockups