My LED Vizio is in a room with a west-facing wall of windows. Absolutely NO viewing issues. I do have a 42" Pany Plasma that was used in that room, and it was actually very hard to watch - washed out. Which is why many of the comparison/buying guides recommend plasma for darker rooms, not bright rooms - because of the black-level performance. My Plasma is now downstairs in a room with no windows, and works fine there.
Good read:
http://reviews.cnet.com/8301-33199_7-57 ... tBody;page
BTW, LED has the same 178* viewing angle as plasma.