I have spent the last few days on the water, and the Sonar+Chart does not lag / pause at all on the Gen2.
The charts can be zoomed in and out regardless of traveling speed and they update almost instantaneously, even on full detail.
I know I was meant to be doing a lot more technical reviewing of the unit these last couple of days, but I was just having too much fun fishing new spots I found with the StructureMap.
It is just amazing how quick and easy it is to use.