I don't think Amazon partnered with Plex. It's basically, you pay for the storage and Plex handles the trans-coding using Amazon's cloud services. So they're like any other subscriber that's buying amazon's on demand computing resources.
Personally as a long time Plex user, I don't see the point. Why download something or rip a Blueray/dvd disc and then upload it to your AWS storage account when local storage is so cheap? Most people have asymmetrical connections. So a 10 or 20 mbps upstream bandwidth is still going to take some time uploading that 20 gb Blueray rip.
Regarding CPU for transcoding, a 5 year old PC running a i3 is good enough to handle at least one 1080p or two 720p streams. You can also buy an nvidia shield and run PMS.
Remember when a bunch of people were screaming about how Apple was going to rat you out to the RIAA for uploading pirated music to its locker system? Yeah this is like that. Right now just sit and wait until it's actually out. Others will test it out to see what happens if you're scared but there is no reason yet to dismiss it since not everything is clear
60$ a month?
200shield + 200drive / 60 = if I use it for more than 8 months better off not using amazon?
EdIT 60$ a year! So umm 8 yrs
Sounds like a legal disaster waiting to happen.