I don't have an SDS1000 or 3000X HD, but the 800 UI-response feels pretty much on par with the SDS2000X HD, as I've stated in my review already.
The SDS2000X HD can get a bit sluggish in certain (rare) situations, but otherwise moving windows like the Trigger Type selection window is fast and smooth. I've just tried and could not find any lag.
For those observing a lag or otherwise strange behavior in the user interface, loading the factory defaults might cure the problem. Alternatively they could just walk through all the settings...
These instruments are fairly complex, and unexpected behavior can be caused by some leftover settings from last session, that are long forgotten by now. Candidates are especially the Acquisition settings and hidden math traces.