The one thing that Xcode 3 does better for me: My main monitor is in portrait orientation. A UI based on a single window with vertical panes doesn't really jive with that.
People have been using paper as a content creation medium for millennia; there clearly isn't anything inherently anti-creation about the tablet form factor. Tablets are only bad for content creation if you consider 'content creation' to mean traditional creative computer software. Photoshop CS5 would be terrible on an iPad, yes, but that doesn't preclude the future existence of equally deep and compelling tablet image editing software (for example).