framebuffers deals with the type of data your writing out of mental ray. For example if you want to write out to a larger bit depth like with .exr format you would want to set it to rgba_fp (floating point) or rgba_h (16 bit) data type.

exr format is a fantastic . Maya 2009 will come with much better support for this format, i suggest it becomes everyones default if your not using it allready.
Read up on it especially if your into compositing.

If you just want to do standard rendering you really dont have to worry too much.

acceleration is just how mental ray will deal with the scene at render time. Read about it in the help files its all there, i allways tend to callibrate my bsp properly if im doing ray tracing. There is a diagnose tab in mental ray where you can see the results of your bsp settings visually, very usefull.

Your renders look ok, I really think you need an enviroment to refract and reflect a bit, clear glass will get all its surface shading values from reflection and refraction, so its important to have somthing there to get a convincing result.

Oh and on render settings, set your max sample level to 2 for production, you need to be rendering at super high res to warrent any higher. If your just testing turn it to 0.

Under raytracing remember that your reflectoin and refraction number setting referes to the number of bounces in the scene not the quality of the raytrace itself. When you have reflections and refractions set to 10, mental ray will refract/ reflect 10 times before returning a sample value. think about how many times it will need to refract or reflect. Start at low 2 maybe 3 and then work up only if you need to.

When it come to blurring reflections and refractoins, i would do that in post if possible, render out refractions and reflections sperately and then blur them. You will need an ID pass as well to have correct matts for each object.