Nigel Kennedy is an amazing violinist and his intonation never fails to impress me. The Walton violin concerto was outstanding, but he plays the viola concerto the same way: like a violinist.
His intonation and interpretation are wonderful in the viola concerto, but he doesn't play heavily enough to make a viola speak. This is especially obvious in the second movement, Vivo, con molto preciso. The sixteenth notes don't speak clearly with a sort of surfacy sound, and just not getting the 'umph' that you expect from a viola, leaving a lot to be desired in tone.
I was also disappointed at times with the balance between the orchestra and soloist. I found myself turning up the volume in places I shouldn't have to in order to hear the soloist, then being blasted when the orchestra comes in.
If you are buying this recording for the violin concerto, I recommend it highly. For the viola concerto I prefer Nobuko Imai's version, or, if you are looking for a budget recording, Lars Anders Tomter's recording under Naxos is wonderful.