PC mode on my f8500 is DRASTICALLY different. the calibration options are super sparse, so unless the tv looks fantastic to you right out of the box, there's no way there won't be a drop in picture quality. FYI, game mode is kind of a halfway point between normal and PC. so if game mode decreases PQ beyond what you want, PC mode will go even further.
I run two hdmi inputs on my f8500, one for games set in 'pc' mode, and the other for all other video. unfortunately, the lag is just way too high for gaming, but I want the best picture quality I can get for anything where lag doesn't matter.
if I had to choose just one, it would be a really tough choice for me.
now, that all being said, the 'PC' mode on the f8500 still looks worlds better than many other TV's. it's not like it totally destroys the picture quality. it's just, why buy a good tv if you don't take advantage of it?
Josh, if you rename the input 'pc' the samsungs will go into pc mode. to deactivate it, name the input ANYTHING other than 'pc'.
Displays: Samsung PN64F8500/JVC X35
AVR: Pioneer VSX-1018AH, 5.1 audio
Sources: HTPC(Mediabrowser), PS3, XBOX360, Wii, Sony DVP-CX995V
Control: Harmony One