I'm using both Apple TestFlight and the original TestFlight, and the original is just such a smoother experience, even with having to add UDID's to provisioning profiles.

Things that are annoying about Apple TestFlight compared to the original:

- itunesconnect, while better than before, pales in comparison to the simplicity of testflightapp

- builds submitted to Apple "take a while" before they're available, testflightapp is instant once you've uploaded.

- managing users in groups seems to be absent