I'm sure dafoomie can tell you the merits of the Vdigi, but I haven't bought one myself.
More importantly, the thing you posted will not work. It's made for a PS2 Linux Kit, and requires you to install their software on the kit to get an image.
You're not going to have much luck with a direct VGA solution to play PS2 games on your monitor since PS2 games don't usually support progressive scan. You could find a TV tuner for your PC that has S-Video inputs pretty easily, but the image won't be that great. Vdigi is probably the best cheap solution for hooking up your GameCube to play progressive scan games, though.
