High-Def Radio?

A couple of my favorite radio stations are advertising that they have new High Definition signals, which is supposed to make the signal clearer, as well as allowing them to broadcast on two different frequencies at once, effectively doubling the broadcast content.
The service is free, and the hardware can be had for $200 or less, so I’m wondering if anyone has this and thinks it’s worth it. I’ve been considering getting XM, but the monthly fee is not too appealing.

What do you guys think?