I finally was able to get my hands on one to try out in a store today and daaaamn. It definitely lived up to all the hype. The build felt real solid, looked even better in person than on pictures and hand a nice in-hand feel. The aluminium casing really does a huge difference. The power button placement was a bit iffy though, and the two button layout was real strange. Though I can see that quickly becoming a non-issue the more you use and get used to it.
Wasn't able to try out boomsound however, as the device had no media except for photos on it, but cranking the volume all the way up and hearing the volume indicator was enough, that shit be loud.
Display was also crisp as all hell and looked absolutely amazing, I was blown away. For some reason it felt like it was miles ahead of the GS4's screen, but I'm sure if I'd gotten to compare the two I'd think differently.
Conclusion: had I not been completely satisfied with my N4 I'd be all over this. Sense was absolutely non-intrusive and looked clean and slick. Hardware felt nice and software-wise it was fast and responsive, though it did have some slight hick-ups. Don't know if that was because it was a demo or what. Still though, major props to HTC for creating such a great device.