I think that much of the initial marketing was aimed directly at the notion of simplified cabling, actually. It was a notion that didn't get much interest from the die-hard home theater crowd mainly because it over-simplified without bringing anything new to the table. The audio portion was no better than SPDIF, which was already pretty darned convenient.

With HDMI v1.1 and beyond, there actually is some value to HDMI's audio portion. Being able to pass eight channels of 192/24 PCM through a single cable is appealing, and having an avenue for a digital bitstream from DVD-Audio and (v1.2 or above) SACD in a standard that might actually show up on players and processors is something that's been begged for since those two formats were new. FireWire can also handle bitstreams for both formats, of course, but hardware support for FireWire was slow to appear and will now begin to disappear entirely (thanks to HDMI's support for the formats and to the slow death of both formats in the marketplace). Bitstream transmission for Dolby Digital Plus, DTS-HD, and Dolby TrueHD has been a sort of nearly-irrational holy grail for many people as HD-DVD and Blu-ray have evolved, and HDMI v1.3 will provide that - although I'm not sure how much practical benefit we'll see from this capability, as HD-DVD at least will still have to do the decoding of these formats internally to support some of the features it offers.