A local high end shop carries the NEC. However, the last time I asked (a few months ago, definitely 2006), the asking price for the 50" display was somewhat greater than $7K. Yikes! MSRP on the Pioneer Elite was/is $5500, and the current Fujitsu 50" is $6500. I'm not clear whether the NEC is a TV or monitor (i.e., no tuner) -- the Pio and Fuji are integrated HDTVs. With that pricing and feature set, no wonder you don't see them very much....
To clear up the Pioneer and NEC glass questions: Yes, Pioneer bought the NEC plasma glass factory a few years back. However, you can tell that they (until very recently, i.e., the Pio 5070 series) haven't integrated: the old (i.e., through 5060/Elite 1130) Pio glass is 1280x768, while the NEC glass is 1365x768. The 61" Pioneer panels (pre-6070) have been using NEC glass -- the resolution and that they don't do 72 Hz (for 24 Hz film-based sources) are the giveaways.
The 6th gen Pioneer glass took a huge leap forward in black level. Pioneer appears to have brought this technology to the NEC factory, because the Pio 5070 is 1365x768 resolution, and I can't imagine them going backwards in black level.
I believe the Mitsubishi 50" plasmas use NEC glass as well. On the pricey side (> $5K for a monitor, no tuner), and I haven't been impressed with their black levels to date. Very good colors however, which is usually cited as a NEC strong point. Local dealers seem to be in closeout mode on the Mitsu 5065, and I don't know what's coming next, if anything.
Hope that clears things up a little,