Many of the WebApp updates are resolutions to previous smaller problems, like keyboard shortcut behavior, compatibility with Internet Explorer 7, and the experience when viewing photo galleries on the iPhone or iPod Touch.
Ars rightly points out that it's nice that Apple not only published the article, but actually detailed what they more often than not sweep under the rug of "this update includes bug fixes and improved compatibility". We likes the info. However, it would have been nice to push out word of the update via Apple's MobileMe News "blog", as RSS notification beats digging through knowledge base articles any day.
If you're a MobileMe user, let us know if any of this makes your life easier!