I came across a couple of super useful DTrace links, and thought I would pass them on:
Brendan Gregg’s DTrace presentation in London:
http://www.context-switch.com/performance/dtrace_workshop01_slides.pdf
Opensolaris student guide (the chapter on using DTrace to debug device drivers is awesome):
http://opensolaris.org/os/community/documentation/files/studentguide.pdf