I have a Riff Raff in the neck of my Gordon Smith Graduate60 (as John mentioned above).
If I remember correctly the GS1's only have a bridge humbucker? If so, I've never tried a Riff Raff bridge pickup, so can't reallt comment on it.
Also, the Riff Raff I have is an older version. I believe Tim winds it differently now? So any opinion I do have of my Riff Raff, may not 'fit' with how the pickup is now winded?