I bought an OEM off ebay for $85, before prices jumped a little bit (probably in response to the $299 sale and added demand)
It's great. Really liking the EOS M with my 16-35mm/2.8. Gives an equivalent focal length of 25-56mm.
I'm not likely to buy it, BUT I'd love to rent or try the new Sigma 18-35mm/1.8 with this camera.
My next purchase is probably the 40mm STM, which can be shared by my FF cameras and the EOS M. Will give a portrait-ish 64mm on the EOS M.