Although I agree and really like rim toning (especially when completely even like that) I haven't seem many of them come back with a star designation. It's not just toning that's looked at too, I believe (I have seen plenty of blast whites with star designations, most PFCAM) but as far as toning it seems like the breadth of the toning and different colors. Rainbow toning is generally seen as the most eye-appealing but I think I like coins like this better, or shades of pretty colors that are evenly distributed. Blues, greens... whatever, but the rainbow toning has always gotten the attention.
Business strike: color/toning/eye appeal Proof coins: stronger CAM contrast "NGC assigns a to coins with exceptional eye appeal (...) Exceptional eye appeal may include attributes such as vibrant, colorful toning; intense luster; or, in the case of Proof coins, especially strong cameo contrast." Source: http://www.ngccoin.com/coin-grading/scale-designations/plus-star.aspx