I just ran a test and the only issue so far is that Outlook 2007 displays the first 2 images, but not the second 2. All images were imported in a zip file, they are not linking to external websites. Maybe the test in Outlook 2007 didn't let the entire email load before taking the screenshot?
Also, Outlook 2007 apparently doesn't like floated images? I easily changed to using align="right" instead of float: right; (just so used to doing this when building websites).
I've had the same issues with images not loading all the way before the screenshot is taken - happens a lot when the images are imported via zip file (seems like CM's servers are very slow to load images). I prefer linking externally for faster display for testing and deployments.
Also, use aligns instead of floats for maximum compatibility.