Although it has front wheel drive and is based on the D3 platform, the Five Hundred is reminescent of the Fords from the 1960's like the Fairlane and Galaxie 500. It has a six speed automatic transmission paired with a V6 engine.
Although a foot shorter than the Crown Victoria, this car is preferred by the luxury Ford buyers for its many amenities. That said, there are very few luxury Ford buyers compared to other brands. This is the product of several decades of crappy cars.
The Five Hundred has only been around for a couple years, so it isn't exactly common on the used car market. You can find some listed on eBay. I think these cars have a good chance of being collectible 20 or 30 years down the line, although that can be a very long wait.