I love it.
It'd be nice if there was a written line under the bottom slider saying how much you are spending now (that changes and is calculated based on the income you put in in the settings and whatever the savings rate slider is at at that time).
Also it would be great if there was a box in the settings to put in current amount saved (like in networthify).
Hope you make those tweaks.
Neat tool though, thanks for sharing.