I think one of the things that you might want to consider is that although there have been some great "new" colour changes released in the last few years, have you spent enough time looking at and working on the older, more established changes?
I'm not just talking about Erdnase here - there's many "old school changes" out there to explore, which in many cases are simpler in execution, more angle friendly and, to a lay audience, just as impactful (heck, do a decent side steal colour change and you'll probably fool most magicians who haven't spent the time on it!). "Simpler in execution" means you spend more time mastering the move than you do trying to learn the basic handling, which results in a better performance.
As for uses, and misuses, of colour changes, I do agree that they should be carefully placed within your routines so that they have a reason for existing. Changes, like all magical effects, need a purpose beyond "oooh, look how pretty!". The real issue here is that thinking about how you're going to use a single sleight or technique is not the most effective way to struture your performance - think about what you want your audience to experience and then select the appropriate routines in order to make that a reality. The important word in that last sentance is "routines" - learn or create individual performance peices and then fit those together.
Ultimately, the more tools you have at your disposal, the better magic you will be able to produce; however, its easy to forget that the magic is NOT about the tools used to create it!
Cheers,
David.