Straight from the product page: "Creative ALchemy (Audigy Edition) restores your Sound Blaster Audigy's ability to process EAX effects, 3D audio, sampling rate conversion and audio mixing for certain DirectSound3D games in Windows Vista." That's right Creative's
extorting charging 10 bucks to fix something that should work in the first place.
Their side of the story is that Microsoft pulled the "Vendor Extension mechanism from Vista's DirectSound implementation," which is what Sound Blaster Audigy relied on to generate EAX effects and other audio processing. Consequently, Creative had to whip up a workaround, which is what they want to take your money for. Without it, your schmancy EAX-enabled sound card will only output delicious stereo sound.
ALchemy seems like a pretty appropriate moniker at this point, since they're essentially making money out of nothing.