I have seen some plasma screens at various TV trade shows, and very nice they are too!
From what I've seen, you seem to be able to view them like an normal TV, close up or at almost any angle. They don't seem to suffer like LCD projection TVs do which have a limited viewing range.
Plasma screens require an optional tuner module if you want to use them like a normal TV. Of course a video or digital box will do fine. Plasma screens have a shorter life span compared to a normal CRT. Black dots can appear when a pixel dies, so you must consider this fact before before buying. (whether you'd actually see this unless very close up, I'm not sure)
Thomson used to offer a trial service to those seriously interested.
There are actually very few manafacturers making these screens, most are rebadged or made to spec. I think NEC and FUJI make a large proportion of plasmas.
If you want a cheaper option, maybe consider a Panasonic 47" projection TV. Sure they don't look so nice and don't give such great pictures, but they are a fraction of the cost.
BUT if I could afford one, I'd get a plasma screen for sure!