Whats the general consensus on OSX Firewall. It's not enabled by default and I never knew the option existed. Is it problematic at all, or prone to slowdowns. I am behind a home router
Its a good idea to turn on the firewall, it doesn't cause any issues or slowness.
However, if you are already behind a home router than software firewall wouldn't matter much, unless you have your machine sitting in DMZ.
If you're behind a home router, you don't need the firewall. You're wasting resources on non-issues if the router has a NAT built-in (which it probably does) and if it's configured.
Beyond that, ipfw2 is pretty robust and you won't notice any resource loss at all if it's running.