The only LCD that I've been even remotely happy with is the Sharp Aquos. And I haven't heard the most positive things about the Panasonic, so am leaning towards the Samsung plasma, myself -- probably the 50A550. But I'm pretty much an LCD snob -- I hate most LCD's that I've seen. But even in the same line of stores (Belmont TV, a local chain), I've only seen them properly set up in one of them (the Laurel store). And I've been disappointed by the picture at Best Buy, too.
The advice I've heard is, if you have complete control over how dark you can make the room (room darkening shades, or shutters, or something), then go plasma; otherwise go LCD.
Oh, and if you're going to go LCD, look at response time (faster == better) and frequency (60 Hz is adequate, 120Hz would be even better, although IMHO unnecessary).