C2D 2.4GHz/Nvidia 320M/4GB RAM
Safari, even with just a single tab open, is really chunky resizing under ML. I can literally count the frames out while I resize, either with the window edges or the green button. I don't recall this under Snow Leopard. If I just have the new tab window open it resizes quickly, but even one tab (anything, youtube, BBC, you name it) will make it chunky as anything.
Non-safari windows are fine.
Windows on the same system is fast...