Have you noticed that you never really see an HD radio demostrated in a store? That cuz they suck.
I've only seen one set up, and it was immediately obvious that HD was not worth paying Ubiquity for their lame technology. HD makes a fuzzy station into a silent station, although you can tune back into their non-HD signal and get your fuzzy station back. Then it adds in a bunch of subcarriers. These might be useful -- weather and traffic, eg -- but they are SO compressed, it is like listening to on-hold music over a cell phone with a bluetooth headset you got out of a gumball machine.
Check that the onboard amp is working, as others have said. Consider satellite or a big iPod if you just want more content. You'll still need to fix your antenna if you get an aftermarket stereo. In that case, I'd accept HD if it came with the stereo, but I wouldn't pay extra for that feature!