I've used an MX-500 for almost two years, and recently upgraded to an MX-700. While I've moved up to the 700, I still think the MX-500 is a great remote - especially for the price offered at BlueDo (which is where I got my 500). The interface on the MX-500 is very user-friendly - a co-worker was able to set his up with very little coaxing from me. You can teach the 500 to control most any system, even if you've never used a universal remote before. If you want a detailed summary of my experience with the 500 and some tips on setting it up, try my
review of it.
The MX-700 uses a different interface for setup - instead of directly programming it, you have to use the Windows software. The MX-700 offers more macro support (basically any button on the remote can store a macro), support for more devices (20 instead of 10), and two extra pages of commands for each device.