I've been playing the shareware version since february and I havent had any problems with my N900. The port appears to be safe and free of major bugs. I havent had any slowdowns or crashes with Duke. Duke Nukem 3D is a very old game so it won't push the N900 hardware to any unsafe levels on its own.

Do not take my word for it because "Individual results may vary" but now you know my experience with it and knowing is half the battle. Afterall, the N900 is a linux pc in disguise and can play pc games from a decade ago easily.