Correction,  I failed to include an important web site to my list.


For case studies check out comparing UNIX to MPE/iX:
 http://aics-research.com

 www.adager.com
 http://www.aberdeen.com - did a study of the HP 3000 and user base
 http://www.hp.com/csy
 Ask Ron Seybold of the HP NewsWire
 Search back issues of INTEREX publications - www.interex.org