Matt, Thats another thing I'll have with me at IISAC08, so you can have a play with that and get a feel for it..
will also have my 300F/2.8 400F/5.6L - one (or both) of which you'll be wanting soon after buying a 70-200F/4L - About the 70-200F/4L, The 2 models differ very slightly, the IS enabled one isn't quite as sharp.. In order of sharpness over the 70-200 L series : 70-200 F/4L, 70-200 F/2.8L IS, 70-200F/4 IS, 70-200F/2.8