Those pictures always bring back memories! I've spent hours on that game long before I ever owned a real Porsche.
+1 for Porsche Unleashed! I got it when it came out and played through the whole thing. It's got far better taste in character than most of the other NFS games and the physics/gameplay are really good for it's time. The front end (menus) is very Porsche-like and has lots of cool historical video footage that plays in the background. It's got a few old magazine ads and stuff to look at as well. The racing is not too realistic, but not too arcade-like either. It's one of the few driving games with accurately modeled cockpits (graphics of the time limited, unfortunately) with a real driver's eye view. The engine sounds are like most fake digital game engines, but they made some effort to make them sound true to each individual car series (the first time I drove my 924S, I was immediately impressed at just how close they managed to get the game sound to the real thing, considering...)
They have just about every Porsche ever made through 2000, except for the 924, 924S, 914-6 (sad...), and really exotic race cars like the 917. They have the LeMans GT1, 935 "Moby Dick" (personally my favorite to drive!), 550 Spyder, 959, 911 GT2 and 3, and other good ones including the Carerra RS, 356 Super Speedster, 928 GTS, Boxter S, pretty much everything.
The tracks are really good, especially the Monte Carlo circuits. They have a course modelled after the autobahn that's banked and everything, plus more standard european countryside type settings.
The factory driver mode is also pretty cool, since you take on the role of factory test driver and drive a bunch of auto-X style courses on the Weissach (sp?) skidpad, do demos for customers, make last minute car deliveries across town, go for afterhours races out and about, etc.
Overall, I enjoyed it alot, and it's about as historically and technically accurate as I've ever seen for Porsches in a video game. Each car definitely has a finely tuned difference from one to the other and each drives more or less like I imagined it might. There's all kinds of upgrades you can buy for your cars that really makes them alot more responsive and fun to drive. You can have as many cars as you want in your garage, so you can leave some stock for the authentic experience and soup others up to win the races hands down (some races are still pretty tough later in the game, though). There's a used car lot where you can find some specific versions of models that were not available in the game's showroom, in addition to some fixer-uppers that may be cheaper to fix than to buy new.
Now if you're a seasoned real life racer/driver and you can't really get immersed in video games, it's going to be boring, since the sense of speed is lacking as usual, but the historical value and Porsche character really set it above most other racing games for Porsche people. It plays best if you have a decent steering wheel and pedals for the computer, though. It's pretty good on an analog controller (XBOX360 PC controller is hands down the best) and pretty tedious on the keyboard.
It's a must have for any Porsche enthusiast if you can even remotely relate to video games.