My favourites are Scarlett, Leighton and SJP. I think I'll pick Scarlett, though.
I don't get the Gisele love. I find her boring. I don't mind the Kristen and Robert one.
The awful ones: Kate Winslet (the subscriber's one was much better), Angelina Jolie (the absolute worst one...not because it's awful, but because it's a red carpet picture! WTF?) and Halle Berry (they made her look washed out).
I personally liked the concept of these covers. It may be repetitive, but it's never really boring (I seem to be the only one).