Well other than needing to be Webstarted (hint hint)...

The flickering red outline when you move the cursor over a square is pretty annoying. I'd prefer a clearer (and more steady) indication that it's a valid move.

The AI seems nicely done: quite competetive. I remember writing an Othello player once, and it was certainly a challenge. Did you implement a depth-based search, or does is just follow some standard optimal rules?

All in all, a good job, I'd say.

Nice implementation. I would consolidate all initial dialogs into a single dialog with radio buttons, or even use default settings and immediately start a game - if the user wants to change the settings, he can do so in the dialog and then restart the game.

Computer player strength is quite good,  but my impression is that it doesn't emphasize the importance of the edge / corner fields enough.