Radar Duker didn't dissappoint once again and has already made a playthrough video of the episode on YouTube. You can check it here, but beware of spoilers - on the other hand, it can be handy if you get stuck yourself. He even found some alternate solutions to other puzzles which I didn't realise were possible, but are completely valid and can broaden the experience!
Furthermore, Mikko Sandt has reviewed the episode for his review-oriented site MSDN, which is the longest-serving source of reviews for Duke 3D custom levels. He gave the episode a neat 9/10 score, concluding:
Despite all the trials and tribulations inherent to a puzzle-centric episode such as this, The Conundrum is a highly commendable feat, putting on display not merely the various rather impressive idiosyncracies of the engine but also the author's creativity in having found such clever ways to exploit them. Your emotions will range from frustration to jubilation, and your overall experience might even be overwhelmingly negative, but even then you can't deny the sheer genius behind The Conundrum.
The full review can be read here.
Among some of the other comments on the episode, the one from Mister Sinister, author of one of the best puzzle-oriented levels for Duke 3D Naked Dash, was particularly interesting:
From the technical point of view this is absolutely brilliant. Visually the episode is very stylish, the subdued beige/grey palette combined with minimalistic yet very diverse and well-tuned texturing works wonders for the map. Architecture is great (as expected), trimming is top of the line and the doors, man, the doors are great! Really nothing to complain about here, this is basically premium design. Well done, dude.
Some of the puzzles legit made my head spin a bit, and some of the mechanics you've managed to find are legit new (mainly talking about the freezer puzzles).
Most of the puzzles here are some of the finest build porn one way or another, use of gate logic is beautiful.
From the gameplay perspective the episode is designed really well. I appreciate how short and to the point the puzzles are, the solutions were clear (I didn't get stuck once, at least not because I didn't know what to do). The addition of dynamic difficulty settings is also really awesome, I wish more people would use this feature. Layouts and architecture are also very well accommodated to the puzzles, nothing gets in the way, nothing distracts from the puzzles. The hints (which I checked out after beating the episode) were cool and easily readable.
Just really good design overall.
Thanks for the reviews, comments and videos, guys, I really appreciate all the feedback!