I share buzzb's dislike of circular grids and their consequent jumbles. In this particular case the absence of annular clues made it particularly difficult since every entry has three consecutive unchecked letters until one gets the theme, which I didn't get until I'd solved around three-quarters of the clues. Some of the perimeter entries are extremely obscure unless one is an expert, and getting the last couple was a slow and tedious slog since I was missing four clues.
I did not welcome this, coming so soon after the jumbles of a couple of weeks ago. Must have taken me around seven hours to solve.
On the positive side I echo buzzb's praise for the clues.