Adding my two cents. This really is a must have. I am using RTM now and am thinking of moving as there are some things in the RTM interface that bother me. Actually the one problem I often have involve multiselect ;-) I sometimes makes changes to more than one item by mistake when I single click an item to view its details and then change an attribute it often affects more items than I wanted.
That being said I want multi select for TD so that I can select a bunch of items and move them to a folder or add a tag. I often enter a bunch of random tasks with topics only and then file them in bulk to RTM lists. I need to be able to do the same in TD for it to be an option for me.