A unique, mind-bending concept done very well. It eases you into the mechanics, it doesn't overstay its welcome, and the later stages utilize an impressive abundance of fresh ideas.
I personally disagree with every "fatal flaw" mentioned in LadyZexion's review, as I actually consider all those "cons" to be pros.
1. I love the fact that the New Game+ is an easier, clearer vision of the game. It gives you a better perspective of everything you went through the first time and is rewarding in its own way.
2. The ambient soundtrack contributed a lot to the atmosphere of the game, and I didn't grow tired of it, as it never got in the way of the puzzles.
3. The triangular jumping arc may look slightly odd, but it suits the mechanics and I always had the right feel for how high and how far I was jumping. It would not have worked as well any if it had been designed any other way.
4. I found the ending satisfying, because it was appropriately simple and thought provoking, a sound reflection of the game as a whole. It created the illusion that the world within the game was of a much more tremendous scale than it is, and it caused me to question my own life perspective. Sometimes the most fulfilling conclusion is something that goes against what you hope it will be.
I will say I didn't understand the inclusion of lives. My best guess is that they were incorporated to discourage the player from solving each puzzle with trial and error, forcing them to carefully consider their every move, but it took away some of the game's immersion for me, and it irked me when I would misjudge a single jump or step on my last life and the game would force me to replay the previous room. It seemed unnecessary and I think the game would have benefited from not having a lives system.
I feel privileged to have experienced Naya's Quest. Upon reaching the end, it's beyond me how anyone could even pull something like this off in Flash.