Easier to install, browsable/searchable/etc catalog.

Also, at openrepos you will be able to create "meta"-repos with cherry-picking of desired apps into single virtual "meta"-repo.

Say:
Alice created appA1, appA2, appA3.
Bob created appB1, appB2 and appB3 (which is forked appA3 with same name, but with different features).

if you enable both repositories, there will be a conflict names/packages/etc.

Charles can create meta-repo called "awesome-apps" and link appA1, appA2, appB1, appB3. so there is no conflict.
When Alice or Bob updates any on linked apps, all users who added ''awesome-apps" as repository will get this updates. Actually this depends on link type: sequential or version.
No unneccecary repsitory updates occures, whenever Alice updates appA3, or Bob updates appB2.

David creates thread on TMO, and states that he created 'sailfish-extras' repo with tested apps. He will link only self-tested and well-working apps here. You enable his repo, and always use tested software. All link are version dependend.

Another example is some-kind of cross-repos dependencies:

Alice created an libA1, libA2 and appA.
Bob created libB1, appB1, and appB2 which uses libA1.

Since Bob personal repository does not contain libA1, appB2 cannot be installed directly by adding only one repo.
So Bob creates meta-repository called, for example, 'appB2-with-deps' and links libA1 and appB2 to it. (now some kind of undefined yet behaviour for default application repo occcures). and when user installs appB2 he actually enabled 'appB2-with-deps' instead of personal repo.