High CPU usage caused by Decor8...
There's some sort of defect in Decor8. Specifically, Decor8 1.07 causes high CPU usage in both Explorer.exe and COM Surrogate (32 bit) when Windows Search (the indexing service) is enabled. This ranges from 30-50% on a dual core machine so the assumption is that it is pegging a single core. If I remove Decor8 and restart explorer.exe the issue subsides. Subsequent boots won't exhibit the issue after that.
Relevant system information: Win 8.1 x64.