No, not really.
Although, you can put anything into your home: repo, that may mess up things…
Repository priorities are without effect. All enabled repositories share the same priority.
That means that “zypper dup” would “randomly” take packages from any repo.
Well, not quite random, it will take the one with the highest version, from whichever repo it comes.
Besides the standard repos + packman, the other few repos that I have enabled don’t have much package overlapping and I usually double-check the updates.
Yes, but “zypper dup” may switch back packages from Packman to the standard repos, which lack support for non-free codecs.
There is no guarantee that the packages in Packman have a higher version.
Actually, many of Packman’s packages are just links to the standard ones (with additional features enabled), so they are exactly the same version.
So the rebuild count will decide which ones will be taken.
You can circumvent this problem by giving Packman a higher priority, then “zypper dup” will take the packages from there.
Or use “zypper dup --no-vendor-change”, so it will take packages from the same repo as they are currently installed from.
I usually update with zypper up, is that something that can lead to problems?
It should normally be ok.
But there can be situations where “zypper up” won’t do well.
It might give conflicts, or it might overlook “updates”.
There was a case like this recently, when the versioning scheme was changes for the Xorg packages.
Instead of 7.6_1.18.3 (which doesn’t make any sense for a long time, but was kept for compatibility), it has the “real” version now, 1.19.1, which is lower than the previous one.
“zypper up” will just not install that “update” (which is a downgrade according to the version number). There were people having problems because of that.
Also, as mentioned, “zypper up” will not uninstall packages that got dropped from the distribution, while “zypper dup” (with or without "–no-allow-vendor-change) will.
There was quite a long mailing list discussion on opensuse-factory recently about the “proper” way to update a Tumbleweed system, and the preferred way is “zypper dup --no-allow-vendor-change” (that option is relatively new btw).
But as I wrote, “zypper up” should be fine most of the time, but it’s a good idea to use “dup” (preferably with “–no-allow-vendor-change” to prevent vendor change and surprises caused by that) from time to time too, especially if you do have problems.
Actually that was the recommended thing since (the new) Tumbleweed exists, before the “–no-allow-vendor-change” was added to “zypper dup”.