I love them! They made something great where Creative failed! I use them on my Audigy 2. Surround sound is fine, no distortion or popping, built in app for testing your speakers, tons of options.
I can't get them to play midis, but I don't really care to play midis anyway (they're usually embedded into somebody's crappy Geocities site along with a bunch of ugly, flashing, animated gifs anyway. Ugh!), so I haven't looked for a solution.
Make sure nothing is on mute (indicated by the gray bubble intead of a blue one below the volume). I've only used them with analog... I'll go look at their site. Also, i had a friend who had nothing but silence after he installed them too. He said something about the onboard audio being enabled in the bios.
Also, click the speaker icon with the "?" beside it. The speaker setup is in there.
I think the last thing I tried on Creatives crap pile drivers was Halo, Completely un-playable, NO sound made it through in-tact, was crackling to hell, and somehow also affecting the games speed. Installed the Kx's, no problem, game ran fine, sound was perfect.