Another really good Ken player is M-tsun, the purple Ken player. I really like his style, even more fun to watch than Aniken, although I agree that Aniken is probably the better player.
As for hard match=ups, I find the greatest difficutly against Ryu and Sagat. These guys dominate the fireball war and in certain respects it’s case of “anything you can do, they can do better.” Ryu can be really dangerous as when he has super, even if he is full screen, if you throw a fireball, on reaction he can throw his and get you.
Good matchups? IMO Dictator is a good match-up, his lack of reversal (barring super) means that if you knock him down, you can jump in for free and set up Knee Bash mindgames. He also does not a particulary strong anti-sir, even his Jumping MP can easily beaten with a Air Hurricane.