Have router, need firewall?

I just got a Netgear router up and running. Its a combination router/modem/firewall. I haven't added any rules to the firewall, but from what I can descern from the literature I don't need to.
I HATE network stuff - it bores the hell out of me and as such I've never been too knowledgable on the subject, so I'm wondering if this piece of kit alone is good enough protection, or whether I need to have a software firewall as well.
Also, these 'firewall rules' or lack thereof are a mystery. Should I add some and if so what/why?
Thanks as always :)

Here's the router specs :
http://www.netgear.com/products/details/DG632.php

You are protected, adding a software firewall will only serve to isolate your machine on your side of the router. Currently the only machines able to establish a connection to you are in response to information you request - such as requesting a web page or joining an online game.

The reason for the rules is to rectify that isolation when you want to receive an inbound request, such as hosting an online game or web server from your machine.

You do so by forwarding the port that information is sent over to the IP of your computer on your local network, if your router then received a network request lets say on port 80 (http traffic usually goes on port 80) it would then know to send that request to your computer.

By setting up rules (Network Address Translation) you can make exceptions for the firewall, but otherwise all inbound requests for information will be discarded as the router does not know where to send them on your local network. (remember that often routers have more than 1 machine connected).

Yeah, living behind a modem/router with hardware firewall is bliss. No more frequent/random access requests (or whatever the technical term is).

However, I still run a software firewall to keep control over any app that tries to phone home. It's really quite pleasurable clicking on the 'deny' button. :P

Zone Alarm or Kerio PF... both have their up sides and down sides...

Is it me or is ZoneAlarm turning into the next Norton?
They should add an "Anti-User" addon next.....

Yeah... I have to reinstall ZA about every 6 months... KPF has about a 8 month lifespan.