We've been hearing about this stuff for awhile now, which I'm always happy to hear about a 'new way' of doing things. There was a news post a few months ago about Phase Change Memory: http://www.techspot.com/news/34593-samsung-to-initiate-mass-production-of-pram-in-june.html

Based on some of the reading I've done, one of the *problems* with this type of memory is the 'phase change' itself takes far longer than the random access time of current DRAM solutions... That makes for more than 10x the latency.

This is probably my own lack of understanding too, but in order to change GST (or whatever material may be used) from a crystalline substance into a liquid, heat must be applied. I remember wikipedia mentioning something like 600*C...... If we're going to be dealing with that kind of heat in our computers, it sounds like there is going to be a whole new overheating battle on the way. That heat has to go somewhere and even if it is delivered on a microscopic scale, it can't possible be cooler than what we use currently.