It's exactly the same as a regular CD, only better sound. Don't count on regular CD's being a thing of the past though. Sony still is being idiots with the rights. It wouldn't surprise me to have another Betamax situation. In that case, I think we're going to see more of DVDA which, IMO, sucks because it's not nearly as good as SACD.
BTW, buy CDs.
The DVDA's I've heard are incredible!
Go to this <a href="http://tinyurl.com/bc7u9">site</a> for a free DVDA.
Here's some more info on SACD and DVDA...
DVD-Audio
The more direct successor to the venerable but outdated CD in the high-resolution camp is DVD-Audio, based on the fact that its foundation is the Pulse Code Modulation system (PCM) that drove its predecessor's success. The primary differences between CD and DVD-Audio center around word lengths and sampling rates more than fundamental differences in execution. The CD was based on the Red Book specification, which, among other things, dictated word lengths of 16 bits and a sampling rate of 44.1 kHz for two-channel audio. The DVD-Audio specification, however, allows for word lengths anywhere between 16 and 24 bits, sampling rates from 44.1 kHz to 192 kHz, and a variety of channel-number options (although 24-bit/96kHz, 5.1-channel mixes will be the most common here in the early stages of DVD-A). DVD-Audio discs are similar to DVD-Video discs, and although a DVD-A's high-resolution tracks are not compatible with standard DVD-Video players, many DVD-As also offer a Dolby Digital mix that is backwards-compatible with DVD-Video players.
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SACD
There is no small amount of irony in the fact that Sony and Philips—the companies that are directly or indirectly responsible for some 500 million CD players and 10 billion CDs in circulation today—chose to move away from their digital cash cow, PCM, and completely rethink consumer audio coding for their version of high-resolution audio. The result is SACD, and with it, a simpler approach to digital audio from start to finish.
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http://tinyurl.com/hjyyu