Pros:
1. Graphics are stunning and cars sound realistic.
2. Driving physics are mostly brilliant.
3. Weather changes are amazing as are wet races.
Cons:
1. The entire game is designed around promoting MTX. it has everything from rigged roulette tickets to time-limited invitations to buy cars, adding that FOMO factor to encourage you to buy credits.
2. The career mode is half-baked. It seems to progress nicely through different calibres of car, then abruptly stops. They probably ran out of time and plan to charge for it later as DLC.
3. FR/MR road cars are overly prone to snap oversteer compared to previous GT's. Some feel practically undriveable.
4. Nearly the entire single player mode is set in this awful rolling-start fashion whereby you start at the back, often 30-40 sec behind the leader and 10 to 18 other AI. It's a chasing game, not a racing game.
5. The AI is frustrating. They are slow but unpredictable - they take weird racing lines and treat you as if you aren't there. It makes them sketchy to pass, and all it takes is one to random punt you or brake randomly in a place they shouldn't, and you'll probably have to restart the race.
6. The interface is clunky and ineffective. Too many menus where you can't do enough. If you don't have appropriate tyres for a race, you can't just buy them there and then. Those on PS4 face several minutes of loading just to buy them and get back to the appropriate race.
Conclusion:
The technical foundations are near-perfect aside from the AI - but there are many flaws in every other area. Polyphony is also notoriously useless at communicating, so I'd hold off for now.