Plasma TV Directly in front of a window

As long as you have good blinds/ curtains so that light hitting your eyes isn't washing out your vision, that should be fine. Probably better than having it somewhere else in the room where it will reflect the window (especially if it's a model without a filter).

For evening viewing, it's moot since the sun's down.

Depends on whether the Bay Window is traditional (Southern exposure, for highest heat gain) or purely decorative little to no direct sun). Either way, you will probably be looking into the light. My L/R TV is mounted across a corner with windows on either side but one faces East and the other North, so no direct light and we watch in the daytime.

Should be fine. But I'd just get some black out curtains to be safe. Can keep them open when not watching during the day, and easily shut them when you want to watch something.

Just search for "black out curtains" on Amazon and you can get an idea of prices.

Out of curiosity I just took a flashlight to the back of my 50ST30 in a dark room and I'm getting light bleed through it. On the left top it makes it look like an edge lit lcd. there's about an inch of that. and on the right side about 5 inches in and 5 down there's a spot that shows up brightly right on the screen like the tv's trying to display it, it's a little larger than the vent holes. It's about where the side bar on Randy's tv meets the picture. On my 54G10 it has just one spot that you can barely see in the same area, upper right. The flashlight is pointing straight through which would be impossible for the sun to do. Not sure what model you're talking about but they can be different according to this test. I gave up on looking for more, I don't wanna know, lol

My VT is directly behind my windows in the living room, 2 dark curtains is all I needed,

how do you watch it with 2 dark curtains covering your tv, thats behind your windows