I was messing around with this last night - yeah I know I said I'd wait, but curiosity got the better of me.
A back to back run with comparing 7 with 8 showed a massive improvement over WRC 7 in terms of handling and feedback. Slob Rally still has the edge IMO, but at first glance there doesn't seem to be much in it at all - it took very little effort to switch between the two, which bodes well for WRC 8
Graphically it's OK - it does the job and can look very convincing at times. However I would have preferred an option on the PS4 Pro to optimise framerate above all else for 60 FPS. That said the 30FPS appears to be rock solid, possibly helped with motion blur, and ultimately preferable to a hit and miss 60FPS.
I haven't tried career mode yet, but one of the things I'm not looking forward is this micro-management and upgrade-tree thing. Don't get me wrong, I know that a lot of people will love it, but it's just not my cup of tea at all. Still I'll give it a go, and if I do hate it as much as I think then I can always run the events standalone, which is mostly what I do on other racing games anyway.
One thing I will say is that the amount of content is unbelievable - it makes Codemasters' offerings look like very very poor value for money with all of their their extra cost DLCs, especially when you consider that Dirt Rally 2 cost more at release for the base version than WRC 8 does for the Deluxe version - at least in my location, and it's all there, it's not being drip fed to us over the course of several months.
All in all I'm very happy, but what I will say about my recent game acquisitions is that while WRC 8 is well on it's way to winning my head, Wreckfest has totally stolen my heart.