I have never been a fan of panning especially extreme where one instrument or vocal is very one sided in the mix. I agree that bass and vocals should be centered in the mix and a little panning of other instruments especially drums can add extra dimension but do not fall into the trap of panning for panning sake.
Re mastering......this is a mixture of good ears and good gizmos. Some folk have the ears but not the gizmos. Some have the gizmos but not the ears and some have ears and gizmos but do not know how to work the gizmos. I suspect that Kevin does not have the proper gizmos or knows how to work the gizmos properly.....cause he certainly has the ears.
Here are a couple of links to articles on mastering for beginners

http://tarekith.com/assets/mastering.html

http://www.tomrudolph.com/presentations/Mastering%20for%20Beginners.pdf

http://www.pcmus.com/AudioTips.htm

http://www.soundclick.com/bands/songInfo.cfm?bandID=687727&songID=5238055