I am using a 16 GB Sandisk mobile ultra SDHC card for the moment
3,85 GB of images and 4,5 GB of Birdseye images on it.

The only things i notice is the start up time is longer with a bigger card in it.
I can't see any delay in refresh the map when i'm hiking, biking or while cardriving.

There was 1 strange thing i noticed when i load compleet CN europe and complete topo germany 2010 the topo germany map don't show up.
when i only put a part of topo germany on it whit complete CN europe there is no problem.

This happend on differnd types on SD(HC) cards.

grtzzzz