Like everyone else, I have bad things to say about the widgets
First the bugs:
1) clicking on the center of the scale widget (without moving the mouse) scales the selection 2%
2) With rotation widget rt:2, the arc of the axes' circles is dependant on zoom. For example, zoom in to where you're 1/2 unit away from the selection, and the axes will disappear
Now the comments suggestions:
1) Ctrl for switching is awful

To quote the log: "[G,S,R] was blocking immediate hotkey access for normal blendering."
Blocking what exactly? G,S,R have
always been taken. And it's not like you can add a feature using G,S,R hotkeys, since those keys are still used when not in widget mode. Another reason it's awful- pressing Ctrl-(Up/Down/Left/Right) to switch scenes or maximize/minimze windows changes manipulator mode.
2) The new middle mouse button constraints for rotation are also awful

. Completely unintuitive- just try posing an armature with it. Please return it to MMB = Trackball
3) Making the lines for widgets thicker and using them as handles as well.
4) Themable options- shading and transparency. To me, shading on the widgets looks out of place, especially when the lines are unshaded and much brighter than the handles (see #3

). I'd prefer to have unshaded, halfway transparent widgets.