I believe native plasma resolution is 768p or something queer like that. My tv is 720p (claimed) but that is where the scaler comes in. Since everything is scaled to 768p, I'd say the Pioneer scaler is very important.
I too am a little wary about everything being scaled too, but I figured that with any other tv there would only be one source that wasn't scaled (ie a true 720p panel would only show 720p source material without scaling it). Since the majority of my tv watching is still SD, that made LCD a poor choice as it has the most problems displaying non-HD source material. I also have a wii, so some of my gaming will still be at 480p unfortunately.
The way my room is set up, I don't normally sit right in front of the tv, so viewing angles came into my choice as well, and plasma dominates lcd in that area. Combined with a much better color ratio and blacks ratio, the plasma became the overwhelming choice for me. Plasma also supposedly does fast motion better as well, and since the majority of my HD watching will be sports, that's very important.
Ultimately, I would have preferred a 40+ inch crt, but those are becoming next to impossible to find. I decided on the best 720p plasma panel on the market. 1080p would be nice, but as there is still a shortage of 1080p source material (videogames and tv shows) and the fact that my tv would only be 40-50 inches made 1080p a luxury I could live without.