I was prototyping a new app idea this week and I thought that it would be a great use case for Swift Playgrounds for iPad. This early stage of development usually consists of quick iterations and Playgrounds make that type of coding much faster because you can skip the compile and deploy steps.
Unfortunately, it seems that the performance of a Live View in the Playgrounds app does not have the same performance characteristics as that same view would have if run natively in a full application. In my case, it was an order of magnitude worse. The main thing I was iterating on in the view was performance, so not having a realistic view of how that view would perform in a real app was a non-starter. So it is back to Xcode on macOS in the meantime.
Hopefully this is something that improves as we get new iOS 10 betas over the summer.