The grouping features added in 3.3 release are great.
The call out option menu that includes options for Merge cells, Fix columns, and Grand summary could be enhanced by including options to "Expand all" groups and also "Collapse all" groups. I think they may work as check box options also in that once they are checked they trigger that behavior (in other words they always appear unchecked on the menu).
This may seem like a small enhancement, but when you have 4 levels of grouping or many groups, it is helpful.