I have heard a number of 5.1 CDs (or should I say DVDs) on my HT system, and they certainly sound nice. Actually it is quite strange, but once you listen to a well recorded 5.1 audio on a (good) HT system, if you listen to it on a 2.0, you will think something is missing. Your mind will play tricks with you expecting a particular instrument to be played for behind you.
In Hindi we have Dhoom and in Tamil Vettaiyadu Vilayadi both recorded in 5.1. Unfortunately these do not seem to be available any more, nor are they bringing out any new 5.1 audio DVDs.
Unless I listen to a really good recording that bring outs 'the subtle time, level and phase differences present on a lot of stereo recordings' as Alan says, I am very skeptical about playing stereo in Neo 6 and such decoding software. This is what many of our cinema halls do when ever there is song sequence. And, believe me, that is a painful experience. In a genuine 5.1 recording, either the instruments are recorded into independent channels, or the time and phase differences are physically coded in. These are things you can actually hear.
Cheers