How reliable is the screenshot mode in 059's client?

Is ss mode 100% accurate to a legit client? I've heard rumors that 059 client users were caught hacking because of noticeable but not blatant differences in their UIs (in ss mode) when compared to a hack-free client.

Right now screenshot mod in 059 is really look-legit, maybe in some old release you can be catched.
You can just create 2 screenshots, first in 059 and second in vanilla, then compare them and look for differences.