I extensively use a few applications from google: mail, reader, calendar. From the beginning I was put off by their design but had gotten used to it.
Then I heard about Google Redesigned which was different and therefore better then the default look. It is quite a solid extension, with only a few very minor kinks.
But then I lifehacker mentioned helvetireader, helvetimail, or helvetical (I forgot which of those 3), and I became very much intrigued.
These are scripts for either greasemonkey or stylish; I chose the greasemonkey variant because I already had greasemonkey installed.
What these do is to dramatically reduce the visual noise on the applications' websites. I copied (copying is not stealing) screenshots from each project's website. Behold the beauty of Helvetica!
Between Google Redesigned (GR) and Helveti*, I am currently strongly in favor of Helvetica. However, GR integration is smoother: the new style is active "before" the google application is loaded, while the greasemonkey scripts seem to wait until the browser finished loading to then activate their style.
Both GR and Helveti* are much more visually appealing than google's default look.