Is it ok to enable proposed updates during Ubuntu's development cycle?

"There is very little benefit to users in using -proposed during the development cycle and such use is strongly discouraged."1

After a new stable release of Ubuntu, testers are encouraged to use the -proposed repository to test Stable Release Updates to help the Release Team decide whether the update should be released to all users. However, during the development cycle, -proposed works differently and the Ubuntu Developers do not recommend enabling -proposed.

During Ubuntu's development cycle, all package updates are first uploaded to the proposed repository. Once the package completes a few basic checks, it is uploaded to the regular repository.

The basic checks include

• Completion of the build on all supported architectures
• Completion of any library transitions (libfoo2 > libfoo3)
• Successful passing of any other automated testing

For many packages, this process can be completed in an hour or two.

If a user has enabled -proposed, they could experience issues with broken packages that have failed some of those basic checks. Generally, it is unnecessary to file a bug about the issue as Ubuntu Developers regularly track which packages fail one of those basic checks.

To summarize, enabling proposed during the development cycle means you have a greater risk of running buggy software and are not really improving the quality of Ubuntu much.

Source:

• Ubuntu Wiki: ProposedMigration
• Original ubuntu-devel mailing list post by Colin Watson

For development releases proposed does not make any sense to turn on.

It is used for automated package testing.

But for stable releases you can enable proposed if you want to test unstable packages and report bugs to launchpad. I see no other reason to enable it.

A better way to use proposed is not to turn it on permanently, but install selected packages that you want to test at the moment.