Not sure if this counts, but I have two of the vertical-styled contacts widgets on one of my home screens (the one just to the left of centre), one for my close friends group and one for my family group, and sometimes the contacts in one of these lists just disappears (the widget itself stays there, just with no contacts in it), and I have to re-assign a group to it.
It's only happened twice since I got it so it's not a majoy problem, just thought I'd say.