The other day I spend the whole day experimenting with various test patterns to work out the best way to set the gamma (this is probably the cause of the mist of most effect you might be seeing). I think most of the problem was to do with the bt1886 gamma using the 10 point to alter gamma at each point and although it added a layer of detail over peoples faces where shadows fall and you can make out freckles, in other situations it does seem to mist things up.
I think the nature of plasma technology makes seeing gamma correctly virtually impossible. The best I could thing of was the PC mode at default looks best and the gamma is at 0.
Across any patterns colour reads the same, white balance is under 3dE in almost all circumstances too.
The patterns I used included 6.5% area windows on black background that THX apparently use, and a 5% area window on a 22% grey background (kind of a plasma torture test), both had a 2.22 gamma with the setting at 0. The difference being black measures 10 times lighter on the grey background (0.06 compared to 0.0068). 0.06 is pretty much good LCD black levels so I guess the 4500/4900 can maintain a 2.2 gamma across various situations but also behaves like a CRT.
The cinema smooth mode 96hz means you need to reduce brightness a few clicks, has horrible dithering and it's debatable whether it's better than just leaving it off and the panel displaying film like a CRT does. It also measured drastically worse white balance, but slightly better black (0.05) on the grey background patterns.
The bizarre thing is on a ANSI test which has 50% of the screen white can still have a black of 0.015cdm²
Apparently Samsungs behave this way but a Panasonic or Pioneer would measure the same black regardless of patterns used.
My advice is leave gamma at 0, and PC is the best preset out of the box (but then I mostly play PS3).