Kerbal Space Program (KSP) will use Vehicle Physics Pro for their wheel and vehicle simulations in the upcoming Unity5-based KSP release.
Felipe Falanghe (HarvesteR) wrote in the KSP development blog about the factors that led to the decision of using VPP. “The new wheels in Unity5 apparently still have a few issues of their own, which makes them very much unsuitable for their job of being wheels… They become unstable if other rigidbodies are attached to the wheeled body, which in our case means the other 100+ parts that make up the ship. Needless to say, that was a problem.”
He continues: “If something doesn’t fit your needs, there is in 99% of cases something you can get that will do the job as you need it done, and once more we turned to the Asset Store and found a very cool package [Edy’s Vehicle Physics] that handles vehicle/wheel physics in not only a very realistic way, but that is also module-based and fits right in with our own part modules scheme.”
Later, after evaluating the documentation of Vehicle Physics Pro, Felipe said: “I’ve been having a look at the VPP here, and indeed it seems to be much more compatible with our existing setup for parts and modules. Even though it’s still WIP, the bits we really need seem to be all there already, plus, the modular design and realistic force model should go very well with the simulation in KSP.”
I provided Felipe with a “kickstarter” script for implementing a generic wheel module in VPP that could be used extensively in KSP vehicles. The VPP-based wheel module can be seamlessly attached to KSP vehicles in any number without any limit (not even the Unity5-imposed 20 wheels per vehicle limit), and wheels can be placed in any position and orientation. Wheels will provide all expected realistic reactions on every situation, with or without gravity.
I’m really proud to see Vehicle Physics Pro considered as the best solution for serious wheel and vehicle physics in Unity 
Can’t wait to try the Unity 5 version of Kerbal Space Program!