It's only hard unless you haven't learned strategies to solve them, and haven't practiced them.
Unfortunately, there aren't many ways to learn it beyond the simplest level, so I've put some free vids up at <a href="http://mathmojo.com/kenken/">http://mathmojo.com/kenken</a>
They help you learn how to solve some of the hardest KenKen puzzles there are.
You're going to love KenKen.
Go figure!
Brian (a.k.a. Professor Homunculus at MathMojo.com )