Short answer: I don't believe so, but I hope you find one because I'd love to have one.
However, if you haven't been following IE development lately, IE's JScript debugging is alot less painful now with IE8; it includes, by default, some dev tools that do pretty much everything that Firebug does with the exception of AJAX debugging (but I prefer a protocol analyzer anyways for AJAX). It even implements an executable console, which includes several of the console.X methods from Firebug!
The profiler, I'm tempted to say, is nicer than Firebug's - simply because it lets you export the results directly to CSV. The actual debugger is as full-featured as JS debuggers get, with stepping/breakpoints/direct input.
Also, I haven't heard Venkman mentioned yet; its the grand-daddy of Firefox debugging (and other Mozilla Javascript). Not as popular as Firebug, but it definitely has its followers.
Lots of good information on this page as well: wikibooks.org/wiki/JavaScript/Debugging