From 1960 through 1986, I've been the lucky audience member of over a dozen Ella concerts (certainly would have gone to more, if they were available - location wise). To this end, I feel that I've developed the essential experience to critique Miss Fitzgerald's performance.
We'll start with near the end first. I heard Ella perform "Flying Home" in Boston around the same time of this recording. I felt like I was viewing the same performance of one of her most fantastic scat sessions - and there have been many - "How High the Moon", "Lady Be Good", "Stomping at the Savoy." "Basella" was a variation of Ellington's "C-Jam Blues" which Ella has done in prior concerts with similar and exciting aplomb - she coaxes the best out of her co-performers and they coax the best out of her.
The first five tracks, backed by the Basie "congregation" (Ella refers to this as orchestra - I think it's a band), are well crafted and executed performances by Ella and the band. The combo sessions follow with a superb version of "Dindi" which offers a far better reading of this song in comparison to her Jobim songbook offering.
There is so much offered in this recording. I would only hope that, somewhere, there is more recorded Ella to enjoy.