They have been around for about a year now. They are quiet and somehow there is something analog about them. Now the only thing I don't like about them is their price. I get them direct from www.cdjapan.co.jp and started with their $10 samplers - you get a normal CD and a SHM Cd for you to compare. The thing they release new pressings on predetermined days and if a title is popular it gets out of print really fast e.g I wanted to get Dire Straits Brother in Arms but to settle for Best of.
Now I know of a guy who thinks the normal CD sounds better then its expensive SHM pressing of a particular title so you might want to buy a "must have" if only to try out. Currently have 3 SHM titles (Dire Straits, ABBA and Spyrogyra). Planning to get Bad Company and Deep Purple when funds permit. Google SHM CDS and you will finds US importers (Amazon has some titles), reviews etc.