I'm a believer in open protocols, but in recent years, I'm also loving Exchange and ActiveSync. I know that's not going to be a popular opinion here. To be honest, I don't know much about how the magic works, but the configuration is simple, the push is reliable, and everything just works. It doesn't drain my mobile and it doesn't lose its indexing and download for hours like IMAP always seems to. And besides, it's mature -- Exchange and EAS have been around for many years.
So here's to JMAP becoming the open standard that replaces that.