A well-calibrated Panasonic TC-PVT50 TV will look exactly the same in almost any room with the lights turned down. Video performance is reliable and predictable, but audio is the exact opposite. Speakers will sound very different in different rooms, sometimes to a frightening degree. AV receivers' speaker calibration systems might help a little bit, but they can never eliminate the problems created by sound reflecting off a room's walls, floor and ceiling. The size and shape of the room, furniture, floor covering, mirrors, windows, and drapes all play their parts in the sound environment.
When I was a hi-fi salesman, I occasionally visited prospective customers' homes and heard lots of hi-fi systems, and one time I heard a pair of terrific $100,000 speakers sounding pretty bad. It wasn't their fault; they were in a sparsely furnished room with floor-to-ceiling windows and a bare stone floor. So sure, the sound was aggressively bright and overly reverberant. Forget the hi-fi for a second; just listening to people talking in that room, you didn't have to be an audio expert to know that no speaker could possibly sound good in that space. The owner of the system was wealthy, and his highly paid decorators and architects were all responsible for creating such an awful acoustic environment. That was an extreme case, but most of the worst-sounding systems are in rooms where decorators are running the show and the clients place a higher value on the way the room looks than sounds. There is no magic technology that could fix the problem.
I've heard "treated" rooms that go too far in the opposite direction, and used a lot of sound-absorbing materials to soften the brightness, but the resulting sound is lifeless and boring. Sure, most rooms fall in the middle range -- not too bright or dull -- but some experimentation with speaker placement, moving the speakers along a wall, or to different walls in the room can be rewarding. Sure, it takes a bit of effort and time, but the improvements can be significant. Moving speakers out from the walls a foot or two can open up the sound. Most speakers sound best when their tweeters are at or near the seated height of the listeners' ears. A carefully placed set of average-sounding speakers may outperform a set of poorly placed higher-end speakers. These recommendations work just as well for iPod and computer speakers as they do for hi-fi speakers.
If you have recommendations or speaker placement tips, share them in the comments section.