I've helped a mid size doctor's office for over 10 years with their IT system. The only value it has for them is managing billing with insurers and scheduling patients. Everything else the system does (tracking lab reports, patient history) is either not practical for the doctors to use or they don't need it. The part about helping with insurers is a business they'd rather not be in but have no choice. The scheduling could be replaced with Google Calendar if not for the tie-in to the data already mandatory for the insurers. Overall the system is something they consider they have to use but a bit of a pain and provides no other value.
Since you have some experience in this field, could you imagine this situation changing in the next several years, so that there is a meaningful ecosystem?
If we do find a solution to the data sharing/privacy issues, its useless without a common core platform that all doctors/hospitals/insurers use. I think we need a core open source platform and have vendors provide value on top of this. I've heard good things about the VA program. Maybe this could be the start of the FOSS platform.