I mostly work with animation loops and a lot of times I offset keys so I can do some follow through and overlapping.
The problem is that since a recent update (I can't recall which one exactly) a bug appeared where the first or the last key of the animation (depends on the direction you offset it) loses its curve and becomes linear. This of course ends up making the animation look weird.
This is especially problematic in cases where the curve is split between the start and the end of the animation and one half becomes linear. It's hard to make that half of the curve by hand without looking weird.
