I had upgraded from 10.8.5 with Server, to 10.9.1 and then 3.0.1 within the past week.
I had 2 issues.
1) network users could no longer login. Fixed with this:
http://support.apple.com/kb/TS5289
2) postfix aliases were no longer working. Fixed by adding /etc/aliases to alias_maps configuration parameter list (in addition to the apple added map).
So, mostly okay and got up and running.
I upgraded from this point to 3.0.2 this morning with no known problems.
Note, I do not use VPN service at this time.