GaN is one, but more to an amp than only that. Need to hear them to properly assess. Have not heard yet, but on the lookout. THe Class D amps I have had for a number of years now still bang my drum so not as motivated to jump as I might be. With new technology, waiting a bit for new advancements to take hold usually pays dividends in terms of value.
I have similar sentiments, however I've not actually had any Class D. I've been watching recent developments for perhaps a year or more and am in waiting mode. I'm in no hurry at all, but will "jump" when I assess things (could be a tricky exercise) as stabilizing.
Forums such as this are valuable in the information discovery process.
I enjoy the quote by Mr Reagan. Some common sense to hang on to.