Version: 2.70 official (win 64)
How to reproduce: Open the provided file, or create any F-Curve that uses the "Stepped" modifier as the 2nd or lower modifier in part of a stack.
Expected behavoir: The F-Curve shown should resemble a sine wave, but flat over every interval of 4 frames. Instead, it looks as though the sine wave function was being carried out after the stepped modifier.
The "Stepped" modifier, being last in the stack as shown, does not appear to read the result of the first sine wave modifier. The problem is the same for noise and generator modifiers as well. This makes it problematic if an animator wants to "step" any kind of noise or function in the f-curve.
Here is a screenshot: