Please refer to John Fowler's superb reviews for most details about this release. I would like to address 3 questions:
1) How is the sound; how does it compare to the CD's?
2) Does the experience of watching the video add or change anything compared to the pure audio of the CD's?
3) Should detractors of this controversial recording consider this release?
1) The sound: they used the TV broadcast mix, which is very different from the CD's mix. For example, on the CD's the singers (T & I) are planted artificially apart in act I, one on each speaker, whereas the video shows them standing close to each other and so they are in the mix (for the video). Also, they couldn't use the post-broadcast patch-up sessions used in the CD's mix. The CD's have the notorious Philips artificiality in other parameters as well, the sound comes across as excessively processed with artificial grandeur. The video mix gives a more natural audio - it had to be straight off the mixing board, as it was a live broadcast, so the engineers were not able to mess up the sound, whereas with the CD's they had years to futz around with it. The biggest difference is that the singers are never overwhelmed by the orchestra as happens very annoyingly on the CD's.
Videos never used the same technology and methods to capture audio as pure audio recordings. Videos from the 80's do not sound like CD's from the 80's, they sound much worse. This is probably the best sounding video from the 80's, because it uses the superior technology of an audio-only recording as the soundtrack.
2) Does watching the video add anything - yes, it adds a lot. Watching Bernstein's theatrical antics on the podium as well as watching the singers even just stand and deliver adds a dimension. I never once lost my concentration, which is an achievement for me in Tristan and a first in this recording. There are interesting details even in the stand and deliver mode. You can see, for example, that in most of act I Behrens conceives of Isolde as dreamy, in another world, transfixed, reminiscing or preoccupied, which goes very well with the conductor's dreamy approach.
3) Can this release win over detractors of this recording? I think I am qualified to answer that, because I always disliked this recording. Bernstein was the first conductor I watched on TV as a child. He has been the only conductor I purchased tickets for his concerts only because his name was in the program - I attended his concerts often in Tel-Aviv. I recall the excitement and anticipation in the biggest record store in Tel-Aviv at the time ("Allegro" on Shenkin St., after it moved from Allenby St.) There was a waiting list, "Bernstein doing Tristan & Isolde!", "when is it arriving?" - it was something. Then, on first hearing, puzzlement, "what is that?" which quickly switched to a rejection of what sounded like an effete, underwhelming recording. Over the years my hostility to this recording increased, as I became convinced that almost everything in the past 30 years has been conducted too slowly. I initially thought Böhm's much quoted alleged comment complimenting Bernstein was meant sarcastically. I now know he wasn't prone to sarcasm, But I don't know if he was sincere. My appreciation of Behrens' artistry has not increased over the years, quite the opposite. The last time she sang the Götterdämmerung Brünnhilde at the MET (in 1997) I was so annoyed I left during one of the intermissions and gave my orchestra prime ticket to a grateful standee. I'm relating all this to establish my credentials as a hater of this recording. The only reason I purchased this release is that after being exposed to so many Tristans that sound like they are being murdered singing this role, watching the clips with Hofmann impressed me - what a treasure, here is a real heldentenor, why did I write him off?
This release completely won me over. All my reservations evaporated. As to the reasons, just read any review by fans of this recording. I don't think it's the time interval of 35 years that changed my mind. Rather, it's the superior audio quality of this release combined with the additional stimuli and focusing of the mind the video provides. This now goes to the top of the list of my favorite Tristans.