It works fine, out of the box... but, it works better with some tuning... so does a Ford Mustang after you modify it a little bit. ;)
The difference (in handling and driving) between a Ford Mustang Cobra (with the IRS, which I am helping a friend build up for fun) and a Jaguar XKR is about 30K worth of labor, suspension tuning, parts replacement, subframe connector installation, and more.
When you're done, you have a car that handles and rides as well as an XKR, but it's cost almost as much and you've spent a whole lot of time on it - and it's still a Mustang with that low-rent interior and all the squeaks and rattles.
I bought an XKR so I wouldn't have to do anything to it but turn the key and go. Same reason I use a Mac - it just works and I don't have to mess with it. And a lot of people are coming around to that view.