Here we go again! Wheaton's performance was fine because he was playing a kid. Get it, a kid??? And the story is written from the adults' perspective and kids (those of us that have them know) they can at times be annoying.
To turn him into some sort of ubergenius, ultra-polite youngster would not have been realistic.
And as for Wheaton's attitude sometimes, hell, I can't blame him. He's been demonized for some crazy reason for just doing his job on TNG. You can't expect him to be a nice guy after all that ridicule.
And I do agree, he should be a semi-regular on BBT. He's a great foil for Sheldon.