Hi,

I like to think of it like this.

extras-devel: Developer playground; I have a package here that just won't work on your device (Quick Clip) and I won't be fixing it in the near future.

extras-testing: What a developer thinks is ready for end-users; I have a package here, TouchSearch 1.3-2, and so far 4 positive votes without a negative

Extras: Applications that have been voted ready for end-users; I have a package there, TouchSearch 1.2-2, and no complaints so far!

Note: there is no karma requirement to go from devel to testing, any developer can promote their app.