Can we upgrade to Samba 3.0.28 safely or will there be issues?
For starters, perhaps it would have been nicer if you were to start a new, separate topic for your questions to keep things transparent here.
I do not know if there are issues in updating, perhaps you should just try it.
On a side note why would you want to do so? Does it have major benefits over the current version? SME Server has limited developer resources and since it is based on CentOS is relies on the upstream packages from this release for a lot of its packages. Since the samba packages are taken from CentOS, if you think there is a major issue please report this in the
CentOS bugtracker and post a reference to the bug in the CentOS bugtracker into a bug report in the
Contribs.org bugtracker. This is the way such changes will be most likely to be implemented the soonest. Like Charlie stated in an earlier post as well.