Originally posted by unixrevolution ...though I don't find my M2 hard to use in low light...in fact I prefer it to an SLR
Depends on the condition. Low light low contrast objects - difficult for any camera, any viewfinder.
But for me, as I mentioned, I had some health issues a few years ago with the result that I have permanently damaged my eyesight, and my right eye in particular is not able to focus at certain focus distances. I still have no problems using the Katz Eye on my K-5, or older Pentax film cameras with split prism (eg. Program A).
But the Leica M9 is unusable unless I wear glasses, and even then it is challenging (gives me a headache after an hour).
My new NEX-5N is a joy to use. Because I don't have to use a viewfinder, I can simply position my (left) eye at the right distance away from the LCD until my eye can focus on it, then I use focus peaking and MF assist.