Rewriting this review thanks to steam deleting it during the recommendation update.
Actalogic's games are flawed gems, I can't emphasize the flawed enough though. Ag Sim 2013 is very temperamental, it lags like crazy on high-end systems and runs great on mid-range ones. The reactive ground is easily the best feature in the game, but is harmed by the odd physics of the tractors, which bounce and hop over the dirt like frightened deer. The big problem with this title is that it was built to run best on a GeForce Titan, yet that fact doesn't get out much anymore - most sim gamers have solid systems but not uber gaming rigs, and the looks of this don't really demand it...so I'd say shoddy programming is to blame here.
Ag Sim crashes often, to the point where the developers added in an autosave feature, which is now the main source of crashes. Some maps have holes in them that swallow equipment tires, others have holes big enough to swallow the pickup truck and the largest tractors. The Tuscany and US West maps appear the most stable, the other two I just avoid now. The game dearly needs a few hefty patches, but the developers vanished several months ago, and the hidden always-online DRM is now proving problematic thanks to server issues on the publisher's end.
If you wanted one of the Ag Sim games off here, I'd say your best bet is Ag Sim 2011, it is more of a resource hog but runs fine apart from issues with the helper AI and problems with parking vehicles and implements in the garages.
Despite the fact I really like this game, I wouldn't wish it on anyone.