Hi Chris,
We use Hyp DRC for a few of its out of the box features. I have not seen any value in developing custom checks, even though every time our sales rep mentions the tool he pushes the fact we can customize . We primarily use the tool for EMI prevention checks, similar to how Ralph uses the tool. My guess is you will be in the same boat. The tool is well suited for nets over splits, plane edge, ref change and so on. Cross talk is better prevented in layout using parallelism rules, and followed up with detailed analysis in Hyperlyx if required. We don't bother with impedance checks or many vias or any of the PI checks as we use CES to set up routing and Hyp PI for real power checks.
I view this tool as a easy tool for PCB layout to self check the design for rule of thumb or good practice techniques. Then use SI and PI tools to determine if problems are real if the PCB designer cannot clean up the problems. Feel free to call me if you still have my contact info. I know this was posted in Feb, did you arrive at the same conclusions?
Jayson