The changes we made to the watercolour should make sure that the stroke continues along the entire length of the stroke from the first input point we're sent to the last, so a sweeping stroke that sends us input points at its very end may look longer than the intention, depending on how the iPad calculates where the last finger impression was. We changed the system to make sure that releasing the touch early didn't suddenly terminate the watercolour stroke where it was at the time, but continued on to that point.
The original problem we had on the Retina iPad related to screen updates, oddly enough - The tool was working about as fast as it always had, but screen updates were not happening so it appeared locked, and it didn't complete stroke processing when the finger was raised.
Glad to hear it has been improved!
Matt
ArtRage UI
Ambient Design.