I originally bought the game around 2012 to play with some friends from work, it was one of my first steam games and I remember it fondly.
I came back to it in 2020 because I wanted to relive it a little and maybe hunt for some achievements. The game is still a fun coop game, the player base is minuscule compared to Payday 2, but you still find people having a good time doing the heists, leveling up, etc.
I know gameplay wise the sequel is much different from its original, and does not allow those hugely OP fun builds the sequel does but if you don't mind the difficulty spike and the game being a bit more serious (just a bit) and even have a friend to play it with you can still have a good time with it.
Just a warning, if you like achievement hunting like me you will very likely need other 3 players willing to help you since a lot of them do require a full party cooperating specifically for it to be doable.
I will likely move on to playing payday 2 since it looks like a good time also!