After reading many of the posts on here, I decided to take the plunge and try an HD Radio.
I have been in the Comsumer Electronics field for years as a consultant, technician and installer of both home and car audio, as well as an avid audiophile.
The Hd I went with is the add on Sony XT-100HD as I have a Sony head that uses this tuner.
Let me start by saying I read a review of this, either on here or elsewhere, that said 1)this tuner is NOT as good as the one in the head unit (as far as analog reception) and 2)that it "eliminates" the tuner in the head unit (I.E. disables it)
NEITHER of these are true.
Let's address #2 first. The reason someone may have thought the internal tuner is eliminated is that the XT-100HD has NO ANTENNA OUTPUT to loop back thru to the head unit. It only has the antenna input jack. So unless one uses a 'Y' antenna adaptor, there is no way to have the antenna hooked up to both the head unit and the HD tuner module at the same time. But the internal head unit tuner DOES still operate.\\
Now, as to the ANALOG tuner performance of the HD Tuner Module, it is, IMHO as good or better than the head unit's tuner. At least close enough to not wory about (and believe me I listen to distant stations...both AM and FM as I live halfway between Cleveland, Oh and Pittsburgh,PA and work in Pittsburgh. And as we all know, HD will not travel much beyond 40 mi. (Although I almost wrecked my car when I actually received WABC-HD 770 AM out of New York City while just outside of Pittsburgh, East, in Greensburg, PA the other day. naturally went in and out of HD while I drove, but I was stunned! This leads me to believe there is no reason the technology can't eventually allow for further distances that 40 miles or so.
Next, let us discuss the SOUND quality of HD....First AM.....as an AM Talk show fanatic (politics/sports/heath, etc) I listen to AM more than FM.....and I can say without hesitation that AM HD is outstanding!!!!!! For all intents and purposes it IS like FM....at least on talk. Yes there are artifacts that would preclude it from competing with the BEST of FM analog done RIGHT (which so few stations do!) but it is a great improvement over analog and, unlike digital TV, simply goes back to analog when you exceed its terrestrial limits. WONDERFUL except lets get those limits in miles reduced!
Fm DEFINITELY sounds better, IF YOU LISTEN FOR MORE THAN FREQUENCY RESPONSE AND TONE. True audiophiles will understand what I am talking about when i say the imaging, dynamic range and inner detail are all far superior to analog, so long as the station is doing, as MattDP so clearly pointed out, passing relatively unprocessed signal to the HD side. Fortunately for me, many of the stations I can get here in Youngstown, Ohio and Pittsburgh, PA do just that. And it sounds great...WELL worth the investment.
Then, of course, there is the added benefit of no static,noise and multipath PLUS the increased program material (I now have a choice of fine arts/classical, blues, oldies,classic rock, 80's rock, country,r&b and some urban stuff i have no use for on the variety of HD2 available in these 2 cities. Only wish there was more talk AM stations (only 2 in Pitts. and none in Youngstown) that do HD.
Let's hope the technology continues to expand and be used by others while RETAINING analog as well.