Better than nothing, and a lot better than the original XP firewall (which did little more than attempt to paper over holes that shouldn't be there in the first place).
SP2 adds an almost useful degree of configurability, but most other firewalls still leave it for dead.
If the alternative to SP2 firewall is no firewall - USE IT!
May be better to look at Kerio (free, but pro features disable after 30 days unless bought) or Sygate personal - or if you like a real toytown firwall with a tendemcy to over-alert, Zonealarm.
Or get the Microsoft/etrust offering -
http://www.my-etrust.com/microsoft/
The firewall is apparently a rebranded and only slightly trimmed version of Zonealarm Pro.
I'm fairly happy with Outpost Firewall (I'm betatesting) but less than happy with the current progress of 2.5 beta - it's got quite a few problems for me at the moment.
Do not ask for beta leaks, as a punch in the mouth often offends
There HAS been a 2.5 leak - and from what I'm seeing, good luck to anyone crazy enough to try it!