Played the PC port a little while after it came out. It was a mess. Constant bugs, lag, and crashing. Since then though they've done a lot in regards to optimizing and stabilizing the game. I'm able to run it at a significantly higher graphic quality without experiencing any lag.
The gameplay is amazing, the scenery is beautiful, the story is intriguing. It makes you actually want to use your focus to read and listen to all the data points, which I haven't experienced on really any other game. The various tribes/factions within the game are also interesting, and it's nice that they're pretty much modeled after various native groups in the Americas. (Carja and Aztecs for example)
The cutscenes and animation quality of npcs throughout the base game is terrible, however within the DLC they are genuinely good. I was shocked by the sheer quality difference.
It is well worth the cost.