I've seen a lot of 'villain' players acting either non-villainy and being all friendly and stuff with no ulterior motive. I have also seen a lot of 'villain' players acting silly, being Disney-evil or just stupid. Jest has skirted around those two pitfalls nicely, from what I've seen. He's nefarious, but not openly so. I believe that is one of the key things to portraying a good villain, and it's something I'm not good at myself.
One thing I think you might throttle back on is Jest's emotionlessness. It's nice and all, but if you overplay it, you're left with nothing but emptiness, and that's boring. You should be careful that Jest doesn't deteriorate into blandness. Doing things with feeling is what makes or breaks a character, to my mind, and Jest is obviously a little lacking in that department. And I'm sorry, but the "I feel nothing" guy has been done over and over so many times, it's getting a little old.
