First, Dark Fire, I think your approach is a bit flawed. I can tell you - and perhaps this is an important one for a sticky somewhere - the *defaults* have been specifically designed to give you good results in average situations. Turning on additional quality options should seldom be necessary except in specific circumstances. Adjusting the base quality slider or AA is often useful, but beyond that you shouldn't generally need or want to mess with things like Ray-traced shadows, "reverse primary rays", etc. The defaults for detail and most render settings should be stuck to unless their function is clear.
The simple fact is that many of the render settings you see now would be considered "advanced" or potentially even not necessary for open access. In the final release you may see many of these settings removed because there simply is little or no value in allowing you to adjust them, and the potential for mistakes, resulting in longer render time or extremely odd results, is very high. It's often better to offer fewer options and good defaults than to offer a world of control but risk overwhelming and confusing people with unknown and hard to explain settings.
Calico, I'll explain these settings to the best of my knowledge, although Matt would need to answer to give full information.
Detail Blending seems to perform additional Antialiasing-type blending between micropolygons (individual rendered scene elements). At the default setting it produces good results in a reasonable time and is responsive to the detail slider. If you reduce it you'll get slightly more noisy output and I believe it's a bit faster. If you significantly increase it (say to 5) you get much longer render times but smoother results for an equivalent main Detail setting. Generally speaking increasing the Detail and/or AA settings would be the best way to increase detail without increasing render time too much. However in certain specific circumstances increased Detail Blending may be the answer to difficult render quality problems like high noise in complex lighting situations.
The Displacement Filter appears to be performing some kind of filtering on the displacement functions, the effect of which is not entirely clear. I would guess that it may be setting the "patch size" of displacement sampling on which displacements are calculated and blended. At larger values the displacement seems less rough, less precise and more prone to errors and overlap. This is a setting I would not recommend adjusting as the resulting output doesn't seem to be an improvement no matter what setting I tried. I'll have to ask Matt for some more info on this one.
- Oshyan