These are not bugs, and in any case two would not constitite "full off bugs". A bug is something that does not work the way it is designed to work, not something that the end user decides should have been there.
Music playing volume via the headsets is governed by legislation in many countries, there are legal limits as to how many decibels you can send directly into the human ear.
I use the N82 myself and there is no issue with brightness that I can tell, if you can't see the screen properly then try choosing a theme with better colour balance between background and text.
As for the comparison with the K850, I too have used SE phones - the Nokia N82 is a "smartphone" which can be enhanced by the installation of numerous software applications, the K850 is not. Also, the N82 other features other stuff not included in the K850, including integrated WLAN and GPS. These are among the reasons for the price.