If you know and like Schumann's 4th Symphony and have never heard the "original version," you really should. It's a gas. Big and little differences all over the place, and even though (for me anyway) the final version is the one to live with, if the original had been the only version, I'd be fine and still adore it.
The first time I heard it was in Orchestra Hall, don't even recall if it was the CSO, I wasn't really assuming there'd be much of a difference (I hadn't read up on it in those pre-interwebs days), just happy to hear it since I loved it.
It was on the first half of the program and Beethoven's 7th was the closer. And the opening chord was probably the most disorienting moment I've had at a classical concert -- I thought I had the order wrong and I was hearing the Beethoven.
I don't remember if I bought an LP of it afterwards back then, 35 or more years ago (and the collection's in storage now) or got to know it further via a broadcast I taped off the air (I just listened to a recent broadcast today). Feel free to e-mail me if you have a commercial recording you would recommend, especially a non-original instrument (ie older) version? (OK, so I'm a dinosaur.)