Just as a qucik summary of the settlement:
Creative was taken to court in California on charges of false advertising over the fact that while the Audigy 1 class of hardware was advertised of being able to process 24bit/96Khz audio, when in reality all internal processing was done at 16/48 and then being upsampled for output. Creative decided to settle it out of court, and this is the result.
If you take up the settlement offer, you will recieve a 25% off coupon good at(and only at) Creative's online store that will get you 25% off of any of their products, as long as the discount doesn't exceed 62.50. If you don't take up their offer, you are still part of the class unless you exclude yourself entirely. By staying as part of the class, you are agreeing that you are satisified with Creative's resolution, and that you can not sue them in the future over the same issue.
The affected cards are Audigy 1 series only, so your card must be an Audigy or an Exitgy that isn't 2nd generation or later(i.e. Audigy 2 and up in all forms and the Audigy Value are not affected cards). You will need to provide your serial number to Creative to get your coupon.
PS The lawyers are getting up to half a million dollars; nice setup, isn't it?