There's an interesting tidbit on the Solaris Internals wiki regarding Dtrace overhead. Under the section "Dynamic Probes," mdb is used to show dissembled code before and after a probe is enabled on a function. Their example uses an AMD64 system; this entry repeats and extends the exercise using a SPARC system.
My review on Amazon, submitted May 11, got ate up for some reason. Today they they found it! It is now available on Amazon's site. My hat goes off to Amazon Support for staying on the case well after I had considered the review lost in the ether. Thanks guys!
Also posted to JavaRanch's Bunkhouse in the Miscellaneous section. If you haven't noticed, by the way, the Bunkhouse now supports searching, so you don't have to guess at categories to find a review of interest.