Hey if it's free, you can't argue with that. Try it out and see if you like it and if it works for you.
I'm really cautious about viruses, so luckily i've only come across two in my time, both were trojans that i downloaded in zip file format that were attached to 2 different irc-scripts. Since i didn't open them (never open something without scanning it first) they were just sitting dormant hoping to run amok. Mcafee found them, quarantined them and i got rid of the files immediately.
As a general rule, and a bit of personal habit, whenever i download something i stick it in a certain folder where files await scanning (if i don't have my scanner already scanning things as i download them - i dont remember if norton does that or not).
As for firewalls, i've had good results with mcafee's firewall, which i had to install on a friend's pc in order to clean it (it had viruses that her kids had downloaded looking at free porn) and once i had the firewall up i found the pc was getting routinely attacked by two different ips on certain days of the week (lagging the connection and probably getting into the system too). With the firewall & virus scanner, the system was cleaned and the security of the connection was restored. Their "backdoor" was closed and the attacks on the ports were stopped.
On my own pc, and the ones i'm building, i'm running mcafee virus scan and putting up the firewall. It works for me.