There's a new recording of Gershwin's Porgy and Bess that is billed as the first recording of the opera as it was performed on opening night in 1935. The published score of Porgy is based on a score that Gershwin prepared before the opera went into rehearsal, and it's very long -- three hours of music, plus two intermissions. During previews, Gershwin and director Rouben Mamoulian cut a lot of material and added some new material; they replaced the prelude to the last scene with a non-musical "symphony of sounds" borrowed from the famous opening of Mamoulian's production of the original Porgy (the non-musical play).
But no score was prepared based on the version that people saw on Broadway, and since then the practice has either been a) Take the original score and perform it uncut, or b) Take the original score and decide what to leave out. Of the previous recordings of Porgy, three are of the uncut score, and one (the first one, from 1951) cuts some material that the 1935 version included while adding back other material that Gershwin and Mamoulian dropped.
I'm surprised that the new recording's solution -- do the opera like it was done originally -- hasn't been tried before. The full score of Porgy and Bess is clearly longer than Gershwin or Mamoulian ever intended the opera to be; they were specifically trying to create a Broadway opera, playing by the rules of Broadway rather than the opera house, and that meant getting the piece down to the average length of a Broadway show, as well as dropping material that didn't go over in previews. Performances and recordings of the uncut score can be interesting, but there's a lot of material in there that was understandably cut from the first performance. For example, the complete score starts with an extended jazz sequence for an out-of-tune piano and chorus chanting "a-wah-doo-wah"; it's very effective, but it's also very long, and the Broadway version understandably cut it in order to get as quickly as possible to the knockout punch of "Summertime." The Broadway version also cuts a lot of the little atmospheric bits for the minor characters, which deprives us of some fine music but also keeps the focus of the opera more clearly on Porgy and Bess.
I just got the recording and I can't yet give an opinion on its quality; it stars Alvy Powell (Porgy) and Marquita Lister (Bess) and is led by conductor John Mauceri and the Nashville Symphony Orchestra, made following concert performances earlier this year. Here's an article from the Nashville Tennesseean about the reconstruction of the 1935 score.
One thing I can say is that I'm annoyed with the Gershwin Estate's insistence that this work be billed (as it is on the cover of the recording) as "The Gershwins' Porgy and Bess." While I certainly appreciate the importance of giving Ira Gershwin credit as a co-equal partner with his brother, it doesn't apply in this case: DuBose Heyward wrote most of the libretto, including many of the best lyrics ("Summertime," "My Man's Gone Now"), and Ira acted as a sort of creative consultant while writing or co-writing lyrics that needed a Broadway touch (like Sportin' Life's songs). Ira himself would have been the first to admit that this was George Gershwin's opera, and the Gershwin Estate should either accept that fact or bill it as "The Gershwins and DuBose Heyward's Porgy and Bess."