We've had the car about a month now and put around 600 miles on it, mostly even split between my wife and me, so I'll do a review on it.
The Jaguar motto since Sir William Lyons has been "Grace, Space, Pace". It's important to understand that, because it perfectly describes the Jaguar take on luxury. It's also important to remember that this is a grand touring car, which is a special kind of luxury and one that about speed, handling, and racking up the highway miles at high speeds effortlessly. Grand touring cars are something that not everyone likes or appreciates.
This era XK8/R and XJ8/R was arguably one of the last Jaguars, depending on where you classify things. Although Jaguar had been owned by Ford for some time, this was still a point where the car was largely designed by Jaguar. In fact, the underpinnings of the XK8 and R still shares a tremendous amount in common with the XJ-S. The rear suspension was one of the big areas that got improved, as well as the brakes, but anyone familiar with those suspensions can see the resemblance.
There are also similarities with the XJ-S in the interior, with a very similarly laid out center console. The dashboard was significantly updated as well as the seats. The car still feels modern for the time, and while the underpinnings of the car hearken back many years, the engine and transmission were modern for the time, with the 4.0L DOHC 32-valve V8 (supercharged on the XKR) and Mercedes 5-speed automatic (ZF 5-speed auto in the non-supercharged). This was a big change from the previous engines. If you teared apart a Jaguar V12 or 6-cylinder, the parts were huge and heavy. Much bigger and heavier crankshafts, connecting rods, etc. than a small block of similar or greater displacement. The end result is a much more responsive engine, and the automatic transmissions of that era had also gotten much less burdensome than the previous GM TH400/4L80E on the V12s and BW66, ZF 4HP22s and 4HP24s behind the 6-cylinders. I abhor automatic transmissions in all vehicles, but in this car it has the highest rating of any automatic I've driven, which is "Tolerable". The shifting is good, in sport mode it's responsive and it doesn't feel heavy or sluggish like most automatic transmissions.
It's important to keep in mind the Jaguar take on luxury when thinking about this car. Yes, the leather on the seats wear faster than they do in a Mercedes or a BMW, but the seats are much, much softer all around. The leather is extremely supple and soft, and that's how basically everything else is in the car. The steering at low speeds is very light but not overassisted. The shifting handle is similarly nice but still has notable detents. Even the buttons and the turn signal clicking is soft, but it doesn't feel cheap or poorly made. All of the buttons, leather, and wood are high quality and very pleasing to touch. Even the shift boot on the hand brake is pleasing to the touch. There are some things that you probably wouldn't see failed on a Mercedes or BMW with only 60k miles on it, but the car should easily make 100k miles in good condition, which is my goal with it. Figuring on 5-8k miles a year on it, that'll last longer than we'll probably want to keep it.
When you compare the XKR against the E55 for example, it's slower, but not enormously so. The power is not crazy, but it is more than adequate, and the car effortlessly accelerates. Remember this is not a car that's about racing, it's about grand touring. Passing people on high speed highways, comfortably cruising at high speeds, etc. In this end, they got it right. Compared to the E55 or GL550, the car is much more pleasant to rack up the miles on the highway, In fact, even though both the Ram and GL550 have better navigation systems and features, I would pick the XKR over the others any day.
My criticisms of the car are few. The differential is making more noise than I'd like it to, which is somewhat normal and it's not enough to be concerning. In fact, one could argue the primary criticism of the engine is that it's too quiet and the primary noise you hear is the supercharger when under a hard load. I would, of course, prefer a manual transmission, but as I said the automatic is tolerable.
Were it left to me, I would have preferred that Jaguar create a clean-sheet V12 in the 4.5-5.0L range instead of the DOHC V8, at least for the XKR. The supercharger, while responsive, is not as pleasing of a sound as a good V12 would have been. A naturally aspirated V12 is an engine better suited engine for grand touring, would have been more responsive, and would've been better sounding. V12s were becoming unpopular around that era though, I think due to a combination of the weight and efficiency. But there's something about a 12.