Duke:
I've been doing a bit of resampling lately. Though, oddly enough, my use case requires the resampling method that you are using. To get smoother, I suggest you try other ResamplingMethods.
Here is what I've learned from my use case:
{"Interpolation", InterpolationOrder -> 1}
Will give you a straight line between our observation points.
{"Interpolation", InterpolationOrder -> 0}
Will give assume that the observed values remain unchanged until your next observation. This gives you a stair step curve.
As I understand it, if you increase the InterpolationOrder, then you will start using curves of the order specified as opposed to lines.
You might also want to try other "ResamplingMethods", but there is a good chance you just need to increase your InterpolationOrder.
I hope that helps.
Have a great and safe weekend.