It's interesting, because I only use iCloud sync heavily with two apps, but I never have issues with with either of them, which leads me to suspect it's partly

It's interesting, because I only use iCloud sync heavily with two apps, but I never have issues with with either of them, which leads me to suspect it's partly a development issue. I hesitate to blame the app developer per se though, because it's also Apple's responsibility to ensure that iCloud integration is easy to set up and difficult to get wrong.