This is an excellent, thrilling and stylish performance, beautifully sung. The music is mostly attractive and enjoyable. Although Vivaldi's music is very popular, his operas have been quite poorly served by the record industry (as have the operas of many other baroque composers). So this issue is especially welcome.
Why only 4 stars, then? Well Bajarzet is an attractive enough piece but to my ear it is as a whole far from Vivaldi at his best. And as an example of baroque opera it also doesn't, I feel, make the top grade. It has nothing like the life, variety, beauty, drama, depth or sheer inventiveness of many Handel operas, for example, and it compares poorly with the two dramatic works of Scarlatti that I have heard (both seem to me to be far richer in invention and emotional impact). Nor does it compare to my ears to Vivaldi's own Juditha Triuphans. So a good record but not a must have piece of the repertory.