I've been using soft synths for a couple of years now (using a MAC so I actually get less latency then on some of my hardware synths believe it or not).
ONe thing to watch out for is mouse clicking. It' will get to you at some point. If you're just getting into soft synths, try to get a hold of some kind of fader box, so you can control your soft synths with hardware faders. Otherwise it's gonna get annoying...
Click Click Click Click Click etc
I HATE IT!
Thank god for Emagic controller.

-ED-