Well, if you're looking for small things... *ahem* One thing that would be really convenient is a shortcut key for inverting, and maybe one to toggle disabled too. The second one's not that bad; if you have to disabled multiple events, you can highlight them all with Ctrl and then disable them all at once. Inverting, though, only inverts the specific event you clicked on.
So, either make a shortcut, or let you invert multiple events at once. After typing this out, the latter sounds much better, actually. Pretty please. <img src="smileys/smiley36.gif" border="0" align="middle" />