There has been several reports mentioning how slow the new Gmail is. In all cases, the problem seems to be cross browser, and of course, cross platform.

Strangely, in my own case, the new Gmail was not slow at all. In fact, it was so fast that I was surprised. It was then when I noticed subtle changes like the custom drop-down list, narrower message rows, the new position of the "Loading..." message, and the "Older Version" link. It even kindly reminded me that Firebug slows Gmail down, and, to fix it, I should disable Firebug for mail.google.com.