It's a wonderful set documenting the peak of Miles' 2nd great quintet. (I slightly prefer the Blackhawk live set but that's just nitpicking.) Very good sonics. Whether or not it is worth the high price, I leave to the individual.
The performances are very good. It is a historic time in music for sure. There is also a Japanese pressed 2 volume set that compiles the highlights from those concerts. The full box set has many repeats, though the interpretations are slightly different.
I don't think the sound quality is particularly great. Ron Carter is mixed so low in the mix you can barely hear him.