Yeah, doesn't match the power of firebug. Wondering what if MS packages some modified version of Firefox as their default browser for Windows? This way everyone would be happy. Quite unrealistic but if they can do some kind of modifications to suit them, I would not mind getting anything which isn't IE.
This is what I've been using but I've found it to be incredibly glitchy, at least on IE8. At times it will recognize an element, sometimes it won't. Sometimes the document fails to load completely in the editor, even though the page has loaded fine in IE.
The main thing I miss with the IE developer tools, at least in 8, is that unlike Chrome their JS console doesn't let you expand the results of evaluating JS expressions that return complex objects. It just spits out "<Object>" or something of that sort.