How are the physics? It's pretty hard to tell by the video, but if you were to place them in a list where would they fall around games like GT5/6, Forza 4, rFactor 1/2, and iRacing?
Hard to tell at the moment, because so many of the cars are still "under construction".
The worst are the ones that are graphics only with placeholder physics. They're just a thing with wheels on it, and they're about as fun as driving a shopping trolley.
The best ones...if those games you listed are a rising scale, I'd say they're probably around the decent rFactor mod level. I'd rate them a bit better than GT/FM, simply because I get more of a feeling of being able to control the attitude of the car with the throttle. It does the edge of grip better than GT, and a little better than FM4. iRacing, for all it's faults and it has some cars that just aren't right, when it IS right it's still better than almost anything else, including pCARS.
The Lotus 49 is probably a good example. The pCARS one is similar to the iRacing one, but it just lacks a level of finesse. Still, the iRacing one got worked on for two years straight so it's hardly surprising. So yeah, pCARS is good but it's not best in class yet.
That said, the tyres are still being worked on, and most weeks we get some demo tyres that are very interesting. They had a brush model that was what was in the Shifts, but they ditched it for the new Seta model that they have now. Don't ask me to explain it, they started talking about it being like gecko feet and my eyes glazed over.
I think they're still experimenting with it a lot to find the limits and where it breaks down, but mostly it feels pretty good. Not as on/off as GT5, more progressive like rFactor2 or NKP.
Career mode I haven't looked into in a while. The idea was to have it calendar based and you enter into racing seasons and progress through the ranks in a manner somewhat similar to a real driver, with invitationals and testing days and the like available to spice things up. Start in karts or low level road racing and work your way up to F1 or LMP-type cars. Someone else can possibly describe it better than me, I haven't really been paying attention.