Justin Lyonand's blog is more about Simulation than SAP, however you still can benefit some from the Content of SEM-BPS, the link is http://www.sapprofessionals.org/?q=sem_bps_learning_hidden_and_useful_stuff.

Actually I have tried PowerSim 3 years ago, it is a very interesting tool. However nowadays not too many companies have a lot of simulation requirements, so BPS and VDT might be their economic choices.