FHIR is a bad answer to a stupid situation.

The fact that it supports extensions and embedded resources is a bad idea. Some of the later stuff is okay, like the layout of patient objects.

Honestly, a big part of the problem is that nobody seems to be pushing back and saying "Folks, we've made all of this too damned complicated...let's just identify useful subsets and make that work."

Also, good luck having any meaningful impact on the discussions if you're not with one of the vendors or can spare the time for bureaucratic bullshit.

EDIT:

A further note on the patient stuff--it looks reasonable if you look at this thing's "Show the result of `GET /patients/<whatever>`". However, the actual spec ( http://www.hl7.org/implement/standards/fhir/patient-definiti... ) kinda hints at a massive headache.