I've heard this new studio recording only once, and that by webcast by WQXR several weeks ago (I've no intention of buying the actual CD set until the effect of the clever hype surrounding its making dissipates, and its price drops accordingly). Generally speaking, we don't do CD reviews here, but this CD set is a special case because of Placido Domingo singing one of the title roles a role his voice type, experience, and temperament would seem to ill-qualify him for and because of EMI's hyping of this studio recording being perhaps the very last of the breed ever made.
Music critic and blogger Alex Ross of the New Yorker got it, I think, mostly right in his brief review for that publication. Wrote Alex:
Domingo pulls off some amazing feats of interpretation in the third act: one line after another is given a heartrending spin. Elsewhere, particularly in Act II, he sometimes sounds oddly wooden, and self-consciously careful in his articulation. The endless love music never goes over the brink into delirium. (Compare Domingo with Wolfgang Windgassen on the legendary 1966 recording from Bayreuth a Heldentenor in heat.) When René Pape comes on at the end of Act II to thunder the role of King Marke, he seems to be giving Domingo a primer in the dramatic recitation of German. Nina Stemme, the Isolde, is a singer of deadly precision, firing off consonants as if they were bullets. But she lacks both the ravishing warmth and the lacerating rage that characterize the perfect Isolde. (She comes closer than most, though.) Mihoko Fujimara and Olaf Bär are miscast as Brangäne and Kurwenal. Antonio Pappano coaxes awesomely voluptuous sounds from the Covent Garden orchestra, but there's something labored about this effort, as if the cast were too consumed by the imaginary burden of making the Last Opera Recording to make a living, breathing one
As I've noted, I essentially agree with what Alex wrote although I would have given a different explanation for Pappano's "labored" reading of the score (I would have called that reading self-conscious, with a slight smell of the lamp about it). And that would be that it's clear Pappano knows intellectually how a correct reading of Wagner's language and rhetoric should sound, and tried his utmost to realize it in performance, but as it's not native to him musically (i.e., he lacks what I've frequently termed the "Wagner Gene") his intuitive sense of it, and his sense of how to realize it naturally, are therefore absent. Mihoko Fujimara, lovely though her voice is here, has Brangäne sounding more like Isolde's naïve younger sister than her wiser, older waiting maid, and Olaf Bär's Kurwenal has none of that character's hardy gruffness vocally or dramatically (he sometimes sounds eerily exactly like Domingo's Tristan) which robs that critical role of its essential central characteristic. As Alex remarked, two roles badly cast.
I would add only that Alex neglected to roundly condemn Rolando Villazón's absurd Verdi-heroic-tenor-aria rendering of the simple seaman's ditty that opens the opera. Villazón's disproportionate vocal grandstanding should never have passed muster in a studio recording, but is something one sometimes (often?) hears in the opera house when a second-string tenor tries to make the most of his only solo (sung twice, or, more precisely, one-and-a-half times) in this five-hour, three-act opera. That sort of Italian-opera-tenor grandstanding makes the short but important little opening ditty sound perfectly preposterous musically and, worse, dramatically, and sets the opera off on the wrong foot right from the get-go.
Bloody Italian-opera tenors!

It's The Music, Stupid!
Peggy
