I noticed STALKER is forced to run as admin each time, this is rather inconvenient for folks like me who don't run admin accounts. I rooted through the registry and turned the option off and everything seemed fine, is there any particular reason why GoG forced it to run as admin? I have the original retail and while I never completed it I don't remember needing admin rights to play there either.

Many of the games are set-up to run that way by default. I think this is done because many game problems (not just this title) are 'fixed' simply by running as Admin, and thus it relieves some of the workload on the support folks. For myself, Run as Admin has gotten several games to work, with no other change. But yeah, if you turn it off and the game(s) run okay on your system, then go for it. Just know that it can help, so don't forget about it as a tool to get a cranky game running.