I believe we were in touch today over mail, but I'm going to repost for others:
- ActiveSync requires licensing from MS; complying with its complicated logistics would just about kill me and my app. Other developers / companies may feel / do differently.
- It's easy to assume that an app developed for Microsoft (the Outlook.com app) does not need to have a license from Microsoft to use ActiveSync.
- I chose EWS over ActiveSync for access to corporate servers. The two protocols are (from my experience) are basically equivalent in terms of access to Exchange specific features.
- The IMAP server behind Hotmail / Outlook.com indeed does not support IMAP IDLE, the industry standard for push mail. It doesn't support even more basic IMAP extensions (e.g. UIDPLUS) that other IMAP services have. It's also fairly buggy. Looks like MS just doesn't take it seriously (could be intentional). Overall, it's been a disappointment.