Ok, just what IS just so bad about XP's firewall?

It seems that ANY security product that comes out always gathers comments like: "Security? Bah, that piece of crap _________ (fill in the blank) isn't worth it..."

I'm hearing the same about XP's built in "firewall" -- I know it's not a *real* firewall. And yet, any scans I run against it seem to indicate that it's pretty decent. Am I missing something? I read in another thread someone actually recommending not bothering with it and disable it.?.? Why? Isn't something better than nothing?