Sorry, I forgot to mention the new Lutron Spacer series of IR controlled dimmers.
Also, the big difference between X10 and Lutron is reliability under load, built in scene selection with both Lutron products (Spacer and Graphic Eye) and far more robust communications between your RC5000 and the IR dimmer (X10 products communicate via an IR to Powerline translator).
[Link: lutron.com]