Sure--ISO 1250 *is* as good as the 5d at 1600. Really. The difference is that the 5d is actually a little more sensitive than its ISO rating, so shooting at 1600 on the 5d is more like really getting 2500. That's a lot more forgiving in the dark.
To be successful with the M8 and 1250, you need to expose perfectly. Not "kind of ok", but perfectly (push it to the right as much as possible). You have exactly 1 stop of error in the shadows, and then noise
However, if you get it right, it's very good, and I like the tonal structure and sharpness at ISO 1250. I also think the latest round of RAW developers are getting very good at developing these files.
http://www.l-camera-forum.com/leica-...tml#post327758
That's not with the latest firmware, and it's also lit by a single bulb at night. More later when I get some time, but I will shoot wedding stuff at ISO 1250.