Cameralabs just published many High ISO sample Images of Canon EOS M, the EOS M have same sensor of Canon 650D DSLR, the image is highly usable up to ISO 1600, noticable amount of noise starts from ISO 3200.
shot settings: JPEG highest quality, 22mm F2 STM kit lens, F8.
See more images here http://www.flickr.com/photos/cameralabs/