Well... i didn't like at all his performance in the part, most of the time he is not in character, just here saying his lines, but i'm a bit indulgent 'cause of the writing and the directing of Lucas. We all know the good acting and dialogues from the OT didn't came from GL: thanks to Kurtz, Huyck, Katz, Kasdan and Kershner (wow! lots of K!!!) and to the actors 'see the work done by Ford and Kershner on Han).
On 1 to 10? 3...
McGregor was a lot more convincing in the part of Obi Wan (and a far better actor...)