The worst! Sure, it plays your files for a few days (if you can put up with the disgusting WMV style compression artifacts, blocky-blurry like really messed up JPG compression), and then every file is watermarked EXPIRED.

To REMOVE 3iVX from your system is non-intuitive. Searching for, and removing the found files doesn't remove 3iVX, you have to follow this procedure;

1. Open HD
2. Open LIBRARY folder
3. Locate QuickTime folder and open
4. Locate and remove the following;
3ivxMediaExporter.component
3ivxVideoCodec.component
5. Drop them right in the trash, empty it, and never, ever admit to any of your friends that you were stupid enough to install it in the first place.
6. Find, download and install PERIAN, it's free and 1,000,000 x better.

Do a little googling about "3ivx problems" and be enlightened. They're just out to make a quick buck and will probably disappear in the near future. They don't even do a modicum of maintenance on their own websites.