A constant, bug filled mess this game offers little to no quality for the price it demands. The only redeeming features of this game being the graphics and sound design. I am speaking specifically for the PC adaptation of this game, there are prevalent bugs and glitches in the game that have been around for over a year, bugs which make the game practically unplayable with friends.
Lets start with the most common, session disconnects every 3 minutes. Yes, when playing in a Horizon Life Session PC players can expect to play for a maximum of up to 5 minutes or more typically 3 minutes before being disconnected and the game trying to find you another session to play in. This is a repeating occurrence that plagues and stagnates player interaction online and practically forces you the consumer to play in solo mode with "Driveatars".
This issue plays into the next which is playing in co-op races with friends is all but impossible. The idea of cross platform gameplay is a nice one, it theoretically allows players of all platforms whether it be console or PC to co-exist in the same servers. However, this does not seem to be a reality for Forza Horizon 4 PC, while cross platform does exist for this game, the connection issues experienced by PC players will make it practically impossible to participate in races with friends from either platform.
(Sidenote, I am not the only one to experience these issues, I have scoured the internet and Forza's own forums only to find an entire community of PC players feeling shunned and unwelcome by the developers as they seem complacent with these issues being prevalent in the game, locking threads listing complaints and redacting statements that hold an overall negative connotation towards the game regarding it's various issues. The developers don't seem to want to fix any of these issues and it has caused a great deal of the playerbase for PC to look into getting a refund.)
Another issue is that the game is coded in a way that makes other consumer brand game pads available for the PC (or at least the one's I have available) unrecognizable meaning for someone using a PC to play with a game pad you have to go out and buy an Xbox One game controller which personally I feel is a bit of scumbag move on the behalf of Microsoft.
So if you want my honest opinion. I do not recommend this game, it's high price paired with game bugs and developer complacency are a major turn off to consumers such as myself. You'd be better off spending that money on better things, like a better game.