Summary: DO NOT BUY IF YOU LIKE FORZA 4!!! This is an entirely different game from previous Forza's and will hugely disappoint Forza loyalists (although you do get a few cars if you played the other Forza's, ironic...) The open world is fun but the driving experience is totally unrealistic and you can't even tune your car! The online aspect is fun but needs a lot of refining; cars jump all over and smashing into other cars is faster than driving a smooth line at times.
Summary: Turn10 did an excellent job at designing this new edition to the Forza collection. The graphics are amazing and very realistic. The open world is huge and filled with many options and tasks to complete. BUT, the game did not meet my expectations. If you are use to Forza 4, you will notice the controls are kept the same and thats where the similarities end. On Horizon, the handling of the vehicles are completely different and unrealistic.
Conclusion: This is just an arcade racer, which is fine if you like arcade racers. For die hard Forza fans it's a big let down. I tried very hard to like it, but it just leaves me cold, Forza 4 still does it for me and I hope Turn 10 doesn't leave it to further horizon. The game itself is I suppose graphically pleasing if you like shades of brown, but the cars are poor and the handling is at best vague. Forza fans probably won't buy this but NFS and Ridge Racer types will.