Certainly not trying to blame the user here and I didn't suggest there was any problem with you providing a specific example, in fact it's quite useful for us to have this info as I have said before. In this case, you also compared to the oil paint which you say is working fine, while other users above have said that the problem exists with the oil paint too, which is more useful information.
We have seen the specific problem you describe happen with the watercolour: It sometimes works slower specifically on the new iPad. When I say we can't replicate it 'reliably' I mean that we have have also observed times when the watercolor runs as fast as on the iPad 2. This leads us to believe that there's something going on in how the processing is happening and we're looking in to it as I said before. I haven't said that I doubt you can replicate it 'at will' which is also a handy thing to know because it helps us narrow down further what might be causing the problem.
All information is handy here, because there's something unusual going on and we need to track down the cause. Hope that clarifies my previous reply.
Edit: Speaking of which - Could you let me know if the closing of parked apps and rebooted as I suggested may help in the previous post makes any difference? This is important for us to know as we're looking in to it.
Regarding the panels: The new iPad has a 2x resolution screen, there's twice as much rendering work going on for the panels and as the device isn't significantly faster it will take longer for them to appear. We may look at either dropping panel resolution or using another solution in a future build.