The biggest issues I've seen haven't been legacy/technological challenges, but almost completely political/incentive/motivation reasons on the part of hospitals

The biggest issues I've seen haven't been legacy/technological challenges, but almost completely political/incentive/motivation reasons on the part of hospitals wanting to build interfaces for many practices. On the part of vendors, many systems Nextgen/Allscripts/GE etc, can often charge an exorbitant amount to build and maintain the interfaces. Even if a practice/vendor is savvy and deep pocketed enough to get past the politics and expenses, then you're at the whim of the competence of the interface teams which can range from incompetent to good, with the average being on the lower end. I've often seen something that should literally take a couple hours, take a year to get completed, if ever. There are bigger initiatives taking place to try address some of these interoperatibilty issues, namely Health Information Exchanges (HIEs), although their economics remain unproven. It's not all gloomy, I can honestly say that in the last 5 years, anecdotally, the hurdle to building interfaces feels like it's getting less and their sophistication and capabilities are getting higher.