Price is good...it's a bit slowish though for a standard prime - with a 40mm, I'd prefer sticking to F1.4 to F1.8 or so. ; I like my 40mm F1.8 in that range. ; Can't help but feel like it's almost pointlessly thin - I mean, I get the whole 'pancake' lens concept on a supersmall camera like a mirrorless system camera, but on a bulky DSLR, a pancake lens doesn't really save you a whole lot of bulk, and to me makes the camera more ergonomically awkward. ; Just stick the body cap on your DSLR and walk around handling it and pretending to shoot with it - that's about how it's going to feel with the pancake onboard. ; For me, a slightly protruding lens on a DSLR makes for a great handhold for the left hand and stabilizes the camera.
Of course, this could be Canon's early hint at a future interchangeable lens mirrorless camera, where the pancake design would make much more sense to me. ; Anyway...those are my thoughts!