tagging images using panes+tagging mode is both quick and easy.
However, here's a couple of observations:
If you tag quickly, it's quite easy to get ahead of MC as it takes (relatively speaking) quite a long time to apply the tag/tick the box. Thankfully, it does a reasonable job of cacheing the mouse clicks, and does catch up with you eventually. Now and again though, MC loses track and so you need to go back and click again. It also means a part of the users focus is taken up with keeping an eye on MC to make sure it's keeping up.
there is a difference of behaviour between 'list type' and 'standard type' panes:
In a list type pane, if all files have the same value, ie, ticked, and you click on that tick, it removes that tag, and if there are no other tags in the list, the files become automatically 'unassigned'. I like this.
Standard type panes work the other way though. If you want to 'unassign' a tag in a standard type pane, you must actually find unassigned down the bottom of the pane and click on it. I don't like this.
While only a small thing, it definately ripples the workflow when working with a combo of list type and standard type panes. It would make things much smoother if all panes could unassign using the same method as the list type panes. I keep clicking a tick in a standard pane to clear it, then when nothing happens, perhaps I got too far ahead of MC, so click it again, nothing happens, again, oh, wait, standard pane, scroll away down to unassigned and click that...
see what I mean?