I should say that of the time of posting this, Duke 3D has been on the App Store for a few hours, and these are just my initial impressions on the game from about 10-15 mins of playing.
just saw this as released on the app store. I bought it straight away after loving wolf 3d on the iPhone, but this is a terrible port, mostly because the controls, from my experience, make it damn near unplayable, I have never experienced such schizophrenic controls. One moment they are totally unresponsive, next duke is running against a wall.
You can play it either with on screen 'analog sticks' or seperate slides on either side of the screen (hard to explain, look at the screenshot.) A red bead follows you finger around the screen, tracking your input. The analog sticks are a joke. Totally useless as there is a bad delay from input to response, and duke is prone to move very slowly, and then jerk in one direction suddenly as you try to get a response. As for the slides, they are not much better, one of the main problems seems to be the games inability to comprehend multiple inputs i.e. moving and turning at the same time. The controls also seem to jam. At least twice in the opening level, the controls stuck, and duke was left running forward, although I was able to turn and strafe.
Otherwise, it seems to be a rather good port, graphically and sound-wise it is crisp and clean, but I did not even have the patience to beat the first level, as the controls are just unbearable. On the one hand I would strongly advise against getting this, at least until they patch the control issues, although I would like to know if this was just me, as I find it rather hard to believe that a port of duke 3d could be so sloppy.
EDIT: Ah, apparently I am not the only one to think so, here is a link displaying the analog problem. http://www.youtube.com/watch?v=iURAvQ1hA8c&e