I also have experienced fps issues, I made a default project just to test it out (the really basic one with the chairs and tables floating in the sky). Right off the bat was getting really poor fps, the same number as you 37.5. I then entered into the console hmd sp 100, and then it was smooth as butter 75fps, but trying to go above 100 would always drop it back down to 37.5. And sometimes if I went back down to 100 it would still be stuck at 37.5. Hopefully epic can fix this.
When it does work it feels really solid though.
Also please add an option to remove the vignette, thanks.