I can now see why this game is considered one of the best if not the best ever. I bought this game 4 times and the first 3(PS2, Wii, X360) I barely played it or the furthest I got was the castle for some reason. Anyway I guess the 4th time was the charm because I am hopelessly addicted to the Steam version. The other day I beat the game and I've gone through Assignment Ada and Separate Ways. I'm currently going through Mercenaries trying to unlock the Handcannon. I've already started another playthrough on normal to mess around with the Chicago Typewritter. Also started a pro run though I haven't done anything besides get to the very first save point lol.
On another note I'm so used to the controls that when I tried another game with my 360 controller I forgot how to play with modern controls I kept pressing start to switch weapons lol.