If you're leaning towards plasma but are concerned about reflection, there's one possible solution for you, provided you plan on wall mounting. If yes, then you might be able to reduce any severe reflection issues by employing a downwards tilt mount, which could eliminate most/all reflection coming from windows and lamps, as the plasma would be slightly angled down towards the floor.
If you have a decent size mirror handy, you can do an experiment of placing it on the wall where the plasma would go, and ideally with one or two people to help, you can then observe any reflection resulting from the downward tilt of the mirror. As one or two people are holding the angled mirror in place, you can place yourself in your various seating positions and observe what you see. If no windows or lights are visible, then there should be little problem with reflection.
Of course, there could still be some
non-light generating reflection, like furniture, rugs, your
, etc, but it will be limited to only very dark scenes on screen. You have to decide how much even that limited amount of reflection still bugs you. Some don't mind it, others might still find it very irritating. different reflectivity strokes for diff.. well, you know.