Andras Schiff has been in the "news" of late, after a series of successful concerts and awards. I have not listened to his Beethoven, but am quite interested in his interpretations of Bach. The video above, for instance, captures a well-done interpretation of Bach's Chromatic Fantasy and Fugue. As a video, it's perhaps better than having been in the audience. With HD quality, it's like you are sitting right next to him. I hope we get more videos as well-done as this.
That said, I was listening to his recording of the WTC 1/2 on ECM New Series. I found my own review of it on Amazon, where I said it was "short of profound." The video above captures well what Schiff's philosophy, I think, is on performing Bach. By getting rid of the piano, and adopting what I'd call a "middle of the road" approach to touch and velocity, he's never too hard on touch nor too soft. The thinking, I am guessing is, that Bach didn't have these extremes at his disposal, either on the harpsichord, organ, or clavichord. Schiff does use dynamics, but they are within a confined space of what the piano is capable of doing.
Likewise, he rarely changes the rhythmic pulse, as I am sure many a piano professor would agree with. His touch is his best asset to the music, I think, in being so light and short that we clearly get to hear each note and I know as an amateur pianist, that takes skill to pull off so consistently.
Where the philosophy sells short, for me, is his decision to not explore the "extremes" in terms of interpretation. I am not sure I have an apt counterexample other than Frederich Gulda, who probably went to the extremes in this regard with his avant garde recording of the WTC in the early 1970s. In so choosing the piano, Gulda explores the extremes of its capabilities in intepreting Bach. It's likely far away from what Bach would have done, but who is to say?
In conclusion, I guess my feeling is if you're going to stray as far away as a modern concert grand as a piano, you might as well take advantage of its full powers and your own creativity in performance. What Schiff is doing, instead, is to strike a happy medium between historical authenticity and his own instrument, the modern piano. You cannot get too critical of his result, but at the same time, there's more in Bach's music than what he's revealing on an emotional level.