I finally got around to installing and trying out NVPerfHUD to get a performance metric today.

Man, that thing is sweet. Very simple and easy to use - much nicer than PIXfW (though it's still falling short of PIX - I'm getting used to PC tools doing that now). If you've got an NVidia card and use DirectX then I highly recommend picking it up just to play with - the docs alone are worth the look, with an extensive look at diagnosing and treating graphics performance bottlenecks in your engine.