I like being able to move tabs between windows seamlessly with Chrome. Safari lets you detach a tab into a new window but that's about it. I don't think you can merge it with another window that already has open tabs or re-attach it. My biggest gripe, which is purely personal preference, is not having the progress bar integrated with the address bar. At least the status bar automatically disappears after a page loads. The feature that will keep me on Safari is bookmark syncing via MobileMe. It's really nice having it sync to my other Macs and iPhone.