A friend of mine has been holding off buying plasma for many years, but since this is likely the last year of the Samsung elite plasma, he is ready to replace his failing 35" tube (Mits that still has the wood around the tube!).
However, when he went into Best Buy today to check it out for the first time, he was disappointed, saying that the set was too dim, and that it also lacked detail....this evident in particular with reference to the display Samsung H8000. In fact, he thought the new Sharp LED looked even better unless you got too close to the set. Also, when I considered buying a new Panasonic plasma at Best Buy in December, I was also disappointed in the lack of detail on the set (used THX Mode), although dimness was not a problem for me.
That being said, I know Best Buy is not the best way to assess a TV, but any suggestions to ensure that the F8500 is actually better when all you have to rely upon is a display at Best Buy? Apparently Best Buy has a no questions asked 15-day return policy, so perhaps that would be a safety net for the 8500. Or could buy fully calibrated and broken-in Samsung 8500 from Value Electronics, albeit returns would be much more difficult, and probably not possible if you just did not like the picture.
Not sure how the F8500 at your local BB was setup. But when you go in again, ask them for the remote. Go into the settings (under Energy) and increase the cell light to 20. Also, disable the Eco mode. Then put the TV in either Standard or the Movie mode, and see if you like it. Another thing that may help is to ask the BB guys to turn off the surrounding TVs to get a better frame of reference.
Hope this helps.