Yes, i'd like to be able to resize the thumbnails as well since one no longer can see previews of the file in the open dialog.
I have mini bridge docked to the upper panels as in this post:
Why was it designed like that, since some people may want the panel docked other places besides at the bottom of the workspace.
Also now that cs6 users apparenly won't be able to preview the thumbnails in the open dialog, mb is even more important in ones workflow.
If you could undock the mini bridge panel to change the thumbnail size and upon redocking it would retain set size, that design might make more sense.