After a week of shooting with the Canon 40mm EF f/2.8 STM lens,I have to say this is one enjoyable little prime. At half the size of the 50mm f/1.8, it focuses quieter, is built sturdier, and is ever bit as sharp.
The 40mm will focus as close as 1 foot. It's not macro (even though Canon says that on the side of the lens), but it is close enough for interesting compositions.
The pancake lens also performed well in the studio. I used it to take a series of product shots.
And finally, with the 40mm twisted into a Canon Rebel T1i, I crashed the Lowepro Summer picnic for some candid work. I also passed the camera around to see how others liked it. In the process, they took a photo of me.
I like to call this lens the "optical body cap" because it virtually adds no thickness to my 60D when packed in the camera bag. I know this type of lens isn't for everyone. But I'm having a blast with it. Currently they're available for $199 US.
You can find more photo tips and "photography how tos" on my Pinterest page.