After selling the TC-1 twice, I bought a G-Rokkor just to enjoy its signature as long as I could.
It's well built, has half click stops from f/3.5 to f/22 (you have access to f/11 now, a handy change), focuses down to 0.8m (which is also the minimum coupling distance of the CLE, may not be a coicidence).
Aperture is not circular, but it's close enough. The tiny front element is deeply recessed into the lens barrel (eliminating the need for the included hood), and the rear protrudes quite a bit - surely looks like something originally designed to be buried into a camera body.
Definitely the same 5/5 aspherical formula and I found no difference in image quality. Pixel-peeping on a NEX shows it to be even sharper than a 28 Elmarit ASPH at image center, but is less even across the field.