Of course he was.
Buffett was willing to walk away from a deal because the taxes would have taken too much of a bite out of it. Fortunately for him, the board gave in and allowed him to structure the deal that he liked, saving him from his own Norquistian response.
That’s not the only time that taxes played a major role on Buffett’s decisions, as recounted by Schroeder. Later in the book (pp. 533-534), she recounts how Buffett chose to structure his investments under Berkshire Hathaway’s corporate umbrella, rather than as part of his hedge fund’s general portfolio, precisely because of the tax advantages.
In fact, as he explained in his 1986 letter to investors, changes in the 1986 tax reform act posed a specific threat to certain investment decisions: