For perspective, below are screenshots of a newsletter in Outlook 2003, Outlook 2007 and Gmail, both with and without downloaded content.
Outlook 2003:
Outlook 2007. Note that looks better/ more readable than Outlook 2003 when blocked content is not downloaded. It looks good with the content downloaded too.
Gmail: It supports even less formatting than Outlook 2007. It doesn't display background images and color at all.
OWA (Exchange 2007 & IE7) renders the same as Outlook 2003, once you enable blocked content. The Outlook 2007 version looks fine if you use Other Actions, View in Browser menu to open it in IE.
Outlook 2007 Has no such "View in Browser Menu".
In an open message, look in the Actions Group for the Other Actions button. View in browser is on the menu that flies out.