I don't remember exactly in what way this wasn't working for me, but it was something related to Carthage and xcodebuild. The workaround, which I use to this day is to define TOOLCHAINS=com.apple.dt.toolchain.Swift_2_3 before calling Carthage.
Even if I did downgrade to Xcode 7.x, it would still add quite a bit of effort on my side, which Apple forces me to do by nagging me to update Xcode.
I think it should work the other way around - Swift 2.3 still default with the option to use Swift 3.0.
In all fairness, I like Xcode - it looks nice, it's fast. It's quite good when it works well - mostly with Objective-C projects.
But the last version has been really frustrating and I think it's a step backwards, which I hope they will fix fast.
Even if I did downgrade to Xcode 7.x, it would still add quite a bit of effort on my side, which Apple forces me to do by nagging me to update Xcode. I think it should work the other way around - Swift 2.3 still default with the option to use Swift 3.0.
In all fairness, I like Xcode - it looks nice, it's fast. It's quite good when it works well - mostly with Objective-C projects.
But the last version has been really frustrating and I think it's a step backwards, which I hope they will fix fast.