Errors after upgrade to Craft 2.5
To answer my own question: There may be some plugin incompatibilities when upgrading to Craft 2.5. This is to be expected, given all the variables. In my case the Placid plugin was not yet compatible, as seen when I put Craft into devMode.

So either:


Wait on the upgrade until your plugins are current, or 
Disable lagging plugins as necessary if you need the bleeding edge.