I recently upgraded to Server 15 on Windows Server 2008 SP2 with 16 GB of RAM and quad core CPU on a Gigabit network (all Windows environment).
The upgrade on the server went smoothly with no noticeable hiccups.
When connecting with FMP 15 the performance is dreadfully slow. Just for the start screen to connect to the server takes forever. Once a file is clicked on, it takes forever to open (too long to time it).
Connecting with FMP 14 on the same PC works just fine, similar to the performance of when it was previously connected to the same files on FMS 14.
I've been making minor adjustments but nothing has helped so far.