The Tureck recordings of the Well-Tempered Clavier are so old that they were originally released on monaural LPs. My first exposure to them -- and to Tureck -- was the re-released, enhanced-to-sound-like-stereo versions. Like this CD, the more recent LPs are based on old monaural recordings that show their age.
But for me, at least, the background hiss is worth it because I am entranced by Tureck's rendition of the Preludes and Fugues. Yes, many of them are slower than more recent recordings, and you can't hear her singing as prominently as if Glenn Gould were at the keyboard (oh wait...), but what I have not seen her critics mention below is her voicing: her ten fingers create three, or four, or even five independent lines in each of the fugues. Give a listen to the C# minor fugue from Book One for an example. Any 4-year-old can learn the four-note subject in four seconds. But this cathedral of a fugue, with its new multiple subjects introduced at the end of the "exposition", is a monster to play contrapuntally. All five voices are heard independently in this recording.
Tureck has the speed necessary to execute the brilliant preludes, as well; witness the D Major, d minor, and Bb Major fugues from Book One.
I confess I am not familiar with many of the other popular recordings of the WTC, so I have little to compare this recording to. However, I recommend this recording. I also recommend Tureck's recordings of the partitas, and the Goldberg variations.