UPDATE: 12/12/2008 

Thanks to Justin Acuff (http://www.justinacuff.net/) and Robert Blum (http://www.luiswatkins.com/5dmarkii/) for helping run this down.

It turns out that 40DShutterCount *does* work on the new Canon 5DMkII.  The only hitch is that the shutter count number won't increment while the camera is on.

For example: say you hook up your 5DMkII to your PC, run the utility, and get a count of 42.

You then take some shots while tethered, and then run the utility again, you'll still get a count of 42.  You can unhook it, take even more shots, hook it back up, and the number will *still* be 42.

Now, turn the camera *off.*  Turn it back on, run the utility, and you should get the correct number of shots.

Good news.   Thanks again to Justin and Robert.

UPDATE: 12/11/2008: I'm getting conflicting reports about the 5DMkII - if you give it a try, let me know the results.  Thanks! 

 Just got my first report from a 5DMkII owner, and unfortunately, it does not work.  Bummer.

Thanks to Robert for the (bad) news.