It's a little expensive for most people here, but I've read a couple people who've used it. The one thing it has that the normal interfaces talked about here is the whatchdog timer; I'm not sure if you want that or not. If you want lighting, I think you'd also need the daughterboard.
For more from people here, I'd recommend the the
LED-wiz (might need 2 per computer if two joysticks + buttons?) or maybe
U-HID. The LED-wiz does lights and one gamepad inputs; no mouse, though, so you might need an opti-wiz if you want a trackball, too. The U-HID is a little more flexible than the LED-wiz, but I'm not sure if as many people has used its LED outputs yet.
Not saying the UGCI is bad; just might be more expensive and overkill for the job. But having a big company (haps/suzo) behind the product might tip the museum, though: the products above are products of different very small companies (apit both with great support).