I think that we should be pushing GUI stuff to the Tcl side of things as much as possible, plus I prefer the current tooltip display down on the lower right. I find that popups right next to the mouse are often annoying.
I agree, except I don't want to push this notion to the point where unpredictable nature of tcl/tk's canvas implementation entirely hampers or limits tool's productivity and provides a half-baked feature. E.g. it's impossible to highlight nlets or show tooltips when trying to patch a cord because tcl/tk's canvas keeps "current" tag on the object that was last clicked on, and yet arguably this is where a new user needs tooltips the most. Selection of nlets and their detection is finicky at best, is very unforgiving (you really need to nail that pixel on the screen to get it), and the list goes on.
Also, the status bar tooltips are really not very intuitive and from the HCI perspective represent a considerable increase in cognitive load over text bubbles because one's eyes have to move at times relatively far from the point with which the tooltip is associated (heck, it is not even that obvious to which object it belongs to if there are two objects located near the cursor). Even a long arrow from an object to a status bar tooltip can cause a considerably higher cognitive load than a co-located tooltip. There is a reason why co-located tooltips exist even in browsers in addition to the somewhat arcane status bar model.
The only context where I see the status bar approach as the optimal way to display tooltips is when the tooltip emanates from a manual invocation that Jonathan pointed out earlier where it makes perfect sense to post it in one uniform place that is not dependent on the mouse position and thus potentially misleading.
Best wishes,
ico