Again, couldn't this just be a temporary situation until the apps are optimized for the + ?
I truly doubt it at this point. The issues are not localized to 3rd party apps. Actually, most of the testing and lag seems to be within the native iOS apps and system. Also, the iPhone 6 running iOS 8 is much smoother, the iPhone 5s running iOS 8 is much smoother. The iPad Air 2 running iOS 8 is much smoother. I would think that if it wasn't a hardware issue, it would have been worked out with one of the subsequent 3 updates, especially iOS 8.1. Though honestly, I don't even think that the phone would be released with lag if it wasn't there for good, to an extent. The only other such situation where an idevice was released with considerable lag is the iPad 3, which ultimately was a hardware issue and was discontinued 6-7 months later