From Chester County, PA, I tend to hear some IBOC hiss from WBZ but not so much that I can't null it out to hear KDKA. It depends on the conditions each night because some nights, WBZ's hiss isn't strong enough to cause problems. Many nights, I can't detect any hiss from 'BZ at all. It just depends on the atmospheric conditions.
KYW, on the other hand, hisses all over the place at my location - adversely impacting 1040 WHO, 1050 WEPN/CHUM, 1070 CBA and 1080 WTIC. When KYW's nighttime IBOC (a.k.a. Soviet-era jammer) is off, all come in here. The frequencies at 1050 and 1070 are nigh impossible to hear over the crappy hiss and now WTIC's previously good signal is buried under high-pitched noise. It will really pi$$ me off next summer during Red Sox season, that's for sure. And, I listen with some good world band radios - not cheapies. So, don't come on here and tell me how it's limited "only" to between 1050 and 1070 because it ain't so. Even good radios pick up the splatter 20 kHz out on each side.
When it comes to hiss on 1040, look to KYW as a culprit just as much as WBZ. They are, by far, the worst offender at my location.
About IBOC, we are in total agreement. There has to be a better way because this isn't cutting it. All this interference for what? So that the 5 people with HD radios who live within 10 miles of the 50 kw transmitter can hear HD? At the expense of everyone else? Because most HD radios won't achieve lock with much less than a perfect signal.
Ironically, CBS radio has the answer for KYW - plopping it on an HD-2 channel of one of the FM stations. Great idea. Now, why not just dismantle the damn AM hashmaker? All it does is cause interference and make the analog feed sound flat. In fact, this is a great answer for most of the big broadcasters. Because FM HD can be viable - unlike AM. Bring back C-QUAM stereo for AM instead!
WCKG in Chicago has WBBM-AM on their HD-2 channel.