Some things I have experienced:
- PCs and servers with Intel GigE network card chipsets (ie, non-Broadcom) attached to 55xx switches will often fall back to 10 or 100 mbps; bouncing the switch interface after the reboot will restore 1000 mbps operation; problem is a known hardware timing issue involving non-Broadcom chipsets;
- If you are going from 4.x or 5.x to 6.1.3 code you WILL have to install 6.0.0 code first before going to the current 6.1.3 code; as NMSman states, read the release notes.