Do Macs need system maint. software and a firewall?

I buried the following questions deep in another thread which is probably why they never got addressed, so here goes with a new thread ...

First of all, I read that Techtool Deluxe is a program that comes with the purchase of Apple's extended warranty which helps identify potential computer problems. Is this like the Norton Systemworks I use on my PC? If not, is a system maintenance program like Systemworks needed on a Mac? Also, is a firewall needed? I recall reading somewhere that Macs have a built-in firewall - am I correct?

I plan to buy my first Mac after Tiger is released, and these are the last few major questions I need addressed while I wait to make the switch.

I have Techtool Pro 4, and it has maintenance, such as basic/medium/advanced scans of your drives and h/w component checks(cache, clock, main memory, processor, etc);volume journaling, data wiping, plus recovery tools that can save you if something major fails. AFAIK there's a firewall embedded in OSX or at least all the ports come closed instead of open. Also with the lack of spyware/viruses for the OS I doubt there'd be much need for any third-party firewall - unless you're networked/sharing with a vulnerable PC

Yeah the only thing that I have done to my computer of 3 years is repair permissions and that's pretty much it. OS X has a built in firewall, so no reason to have a 3rd party firewall. I've never had any problems with either of my OS X machines and they are online 24-7.