Seriously, the only info obtainable from RE'ing this would be the power & thermal stuff that we're trying to get documented now. I think everything else is already either running in the open drivers or being worked on already. This isn't a standalone library, it's an API into a big honkin' binary driver, so RE'ing it would take some work.
Fan & temp info for 5xx and lower GPUs (and some early 6xx parts) would be pretty easy to figure out, but Alex has already talked about that (third-party temp sensor/fan controller chips hooked up by GPIO lines) and devs are already using the info.
Midway through the 6xx family we started rolling in a lot of changes to that area, including adding a fan controller on-chip, and (a) things got more complicated, (b) things started changing from one chip to the next. My guess is that we'll have documentation out first.
As a condition of installing or using the driver you agree not to reverse engineer, disassemble, bend, fold, spindle or mutilate it (although you are allowed to copy it), so obviously none of the fine Phoronix readers would be doing that anyways, right ?