I saw the 2D version. It was good (particularly the performances by Karl Urban and Olivia Thirlby), but....
The film was claustrophobic, with over 3/4 of it taking place inside a single building. This did not leave room for any exploration of the futuristic world of Mega City One.
There wasn't much humor. While the lack of Rob Schneider schtick was a good thing, the Dredd comics had a lot of twisted British humor which was missed.
While 3D may improve the action, it won't improve the above flaws.
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Ted J. Kilvington, Jr.
*****
"I still have that comic, only now it's in liquid form!"