So, after playing the demo, some impressions.
The menues are an improvement over the old ones. The game looks sleeker and, overall, appears more streasmlined and stylish on first glance.
The graphics are, as most know, vastly improved over FM3. The lighting is probably the biggest improvement, especially in cockpit view. It seems quite a bit more realistic than FM3, in my opinion. Also, most car models seem more detailed, which is especially evident if you get closer to an AI car and get a better look at the tail lights, for example.
Soundwise... Oh my god. Whether it's the Eliminator's roaring V8 or the screaming Pagani V12, the game sounds pretty darn impressive. But, aside from the engine sounds, the tyre squeals have also been improved, in my opinion. FM3 was good in that regard, so the difference isn't that big, but it's better than before, I think.
Damage also seems improved - mechanical damage, at least. It seems to be more sensitive than in FM3 and parts seem to get damaged both easier and more locally.
The handling, on the controller at least, is probably the biggest improvement over FM3. Proper throttle control now seems far more important than before, the cars tend to go into oversteer or understeer a lot easier now. It's also harder to catch a car if it oversteer, harder to recover from understeer and it seems more difficult to compensate for mistakes this time around. Also, things like body roll and weight transfer feel much more pronounced.
What can I say, there's not that much new stuff to report since Gamescom, but it feels great.
By the way, I like the "infinite cars mode". Lookign forward to using that on Fujimi Kaido.