A while ago, something happened to increase the signal strength, so some people can now get at least some of the NBC HD feeds without modifying the skew.
The audio setup on these channels is weird. Most channels will either have an MPEG stereo stream or a Dolby 5.1 stream, or both. These channels have three MPEG stereo streams, except they're not normal stereo streams that carry the totality of the sound in left and right channels. They're carrying a 5.1 channel set, paired up in the way that they appear on the analog outputs of a sound card. One is front left and front right, one is rear left and rear right, and one is center and subwoofer. The problem that you may encounter is that the front left and right don't necessarily carry all the sound necessary to understand a program. Sometimes, the production will be miked such that the dialog is only in the center channel, not audible in the left and right channels at all, and conversely the other sounds will only be in the left and right, not audible in the center channel at all. Not all programs are this bad. But, you can't always listen with the default sound channel that your receiver picks out, sometimes you have to try all the channels to find which one sounds best. There's no consumer receiver that reassembles the sound correctly from this style of transmission.