Bajazet is a "pasticcio", witch means that, as we know, difers from a regular opera, by the inclusion of arias from previous works by vivaldi,(Olimpiade, Farnace, Motezuma, etc...), witch are used for the "positive" caracters, and other composers scores (like Giacomeli or Hasse), for the "negative" caracters, and some original music as well.
Some areas were performed in the 1730's by the castrato Farinelli.
The plot is very simple as one should expect from a pasticcio, but serves the music perfectly, creating a very deep atmosfere. I dont know if is the fact that i assisted the concert before i had the disc, but i find it very moving (the happy end is ruined by the suicide of Bajazet).
Even if you already have some of the music wich is included, does not mean that is boring, by all means, that you listen to them again in this interpretation. Otherwise, If this is your first baroque opera, im shure you will like it more and more, as you listen to it!, as it does have some of the greatest late italian baroque music ever created.