I got one of the PlayStation 2 Street Fighter joypads a few days ago. It works extremely well with Street Fighter games (of course). The controls are laid out much like the Saturn controller, with six buttons on the face, and two triggers.
It's very comfortable in the hands. It feels a bit different than most controllers for Saturn (or most systems in general) because the triggers are angled outward a little more than usual, so your fingertips rest comfortably on them. This is fine for Street Fighter games where you don't use the triggers frequently. The digital joypad on it is responsive and feels "just right"--not stiff, and not loose. The overall quality is great, and the collectible packaging is a nice bonus.
In general, I would say a good-quality arcade-style joystick would be better for this type of game than any joypad. Still, if you don't have the money to plunk down for a joystick, or room to set one up, then I would certainly recommend this joypad!