Try resizing a heavy-weight application such as Firefox 3. When using Metacity, what you'll see is that the window bounds and the decorations will move seamlessly with your cursor. The contents of the Firefox window will not update that fast, so you'll see 'empty' grey space when you increase the size. However, when using Compiz, what you'll see is that the window bounds and decorations will actually wait a long time before moving along to the new location of the cursor. It seems that Compiz waits for the contents of the window to be repainted for the new size, before it moves the window bounds and decorations. Metacity's way of 'cheating' actually makes the system look a lot faster than it is, because the resizing operation works seamlessly. With Compiz, window resizing becomes a tiresome process, because you constantly have to wait for the window to catch up with your cursor. If you let go of your mouse button too soon, the window might not even resize at all.
Resizing is a well known issue. We're hopefully getting this sorted out once and for all during the Compiz 0.9 development cycle. I'm closing this bug because we're moving bug trackers. You're welcome to re-open at bugs.opencompositing.org, but this is a problem we're well-aware of. Sorry for the inconvenience.
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