This is a great collection, and whether you love it or not depends on whether you like Brendel's style. Even if you are familiar with his playing, you're likely to be surprised by some of the items: the early Beethoven Concerto No. 4 is full of relaxed lyricism in a performance of great freedom, quite different from Brendel's good but more strait-laced later recordings with Haitink, Levine and Rattle. His Liszt Piano Sonata has always been celebrated on Philips, yet I think it's this earlier recording that shows Brendel at his best - full of passion, virtuosity and dramatic flair, but always keeping the work's structure in clear sight. Very impressive, one of the best recordings of the Liszt Sonata you're likely to find.
Other highlights are the Schubert Sonata in C Minor and the Mussorgsky Pictures at an Exhibition, both of them more dramatic and powerful than his more restrained Philips remakes, as well as his excellent collaboration with I Solisti di Zagreb and Antonio Janigro in Mozart Piano Concertos 9 & 14. Also listen out for his no-nonsense Chopin Polonaises and surprisingly vivid Liszt Paganini Etudes.
There are some disappointments - I've never been a huge fan of Brendel's Beethoven Sonatas, and like his Philips cycles I find these a bit hit-and-miss. It's fascinating to hear his first thoughts nonetheless. All in all, a great collection both for Brendel and more general music fans alike.