Just a quick update.
Installed the v1.49 patch, savegames still work, and it doesn't appear to be so aggressive with the enemy AI. A few shots still hit me but it's not as bad as 1 guy 200 yards away with a pistol killing me with 2 shots while I'm hiding around a corner with v1.50!
Also tried the crack for v1.49 and the AI is the same as with the original EXE, so I guess the v1.50 patch must have upped the enemy AI, either by design or by mistake?
Sticking with v1.49, it's easier