Until yesterday I hadn't. According to this document it really is part of the Windows SDK - but it wasn't on my system. As it turns out, it doesn't install on x64 systems.

The appropriate files can be found in WinSDKNetFxTools-WinSDKNetFxTools-x86.0.cab in the Windows SDK DVD Image. Just extract and rename.

Wpfperf.exe links to a native x86 dll. It will not function correctly as an x64 process so we need to force it to run in x86.

corflags /32bit+ wpfperf.exe

This works, but in order to profile any applications, they too will need to be running in 32bit.

Update: actually this doesn't work terribly well, WpfPerf frequently crashes. I'm downloading the Windows SDK Feburary update to see if there's an updated or an x64 build available.