I disagree with maders opinion.
A few days ago the only problem for users switching sometimes between stable and nightly was that the update procedure as described did not work. System still claimed no connection to repo and as a follow up the not updated pvr version stayed disabled.
Then I had contact to relkai here in the forum. He changed something and told me to download the nightly tar file again. Did that and installed the tar file. Then CE repo and CE nightly repo can both be reached again and all addons will be updated.
Some other Users had the same problem and could solve this with downloading newest tar files and doing a stable nightly stable or a nightly stable nightly change.
CE 9.0.1 stable/nightly both running like a charm used with my several devices.