I hate it!
Get Spybot and Ad Aware and run them both (separately).
Run Spybot at least weekly thereafter, and Ad Aware daily.
It helps. A LOT!
That said, I ended up having to wipe my HD because I tried to manually remove gator and missed a few files. Reformatted and a NEW XP install, and no more problems.
I had problems with Gain/Gator. I could always tell when it was loaded without my consent onto my machine, because it would slow me down to a crawl. SpyBot Search and Destroy did a very good job in removing it, but soon I would go to a website that would put it back on my machine again. Since SpyBot added the "immunize" feature, I haven't had the problem again. So get SpyBot Search and Destroy, scan for and delete the spyware, and then click on the "immunize" button.