I love m/c music. Looove it! Two-channel is great, and I wouldn't give it up, but I consider m/c music to be something of a treat. My favourites of my collection would include terrific albums like The Beatles' Love, Blue Man Group's Audio, Dire Straits' Brothers in Arms, Porcupine Tree's In Absentia, Queen's A Night at the Opera -- and the surround implementation on them is done superbly. It feels like you're inside the music or that you're on some crazy, kaleidoscopic ride. It doesn't replace 2-channel music, but it's a fun alternative (and isn't that what this hobby is supposed to be -- fun?). Give it a try. You might like it, you might not. Part of the joy in life is trying new things.
3dB, it depends on what you mean by "realistic". If you mean, will it sound like you're at the gig? Depending on the mixing, the quality of the recording, and in the intent of the person mixing it, it might. If you mean, will it sound like you're in the recording room with the band? Again, depending on the mix, it might.
There are some m/c live albums, and I would assume they're mixed to sound like you're at the gig: the music coming from the front three speakers, ambiance, echoes, and crowd noises from the rears. So that would be "realistic", I think. But the m/c albums that place you right in the middle of the music? Not "realistic" I guess, but fun definitely.
cheers,
supervij