Regarding entertainment centers:

I have seen some amazingly cool cherry wood entertainment centers meant to house an RPTV. Basically, they cover up everything except the screen. Looked amazing.

I know of at least one Spot member who made a deal with his wife based on getting a new entertainment center along with the TV. If you need links I can dig them up.

one of the things that I noticed was that the HDTVs had no gaps between pixels (bad terminology, I'm sure) -- it was a solid wash of color, whereas the NTSC TVs had a lot of black mixed in with the video. I'd noticed this before, but I'd never noticed how prominent it was. Anyone know if that lack of black will also exist when viewing NTSC?

I think what you're seeing is the difference between an interlaced picture that includes visible NTSC "scan lines", and a line-doubled progressive-scan picture that eliminates the scan lines.

Most HD sets will eliminate the scan lines, yes. That's all part of the image processing and line-doubling circuits. Looks really good when it's done right. Similar to looking at images on your PC monitor.