Sooooo...I've spent about the last three days just shotgunning this mod, since I realized I never actually got past the first area all those years ago (chalk it up to Mass Effect 3 coming out around that time...

), so now I'm ready to give my full feedback!
(Note: I'm still not sure if I'm completely "finished" with the mod yet, since I'm still in the Wheel part but just got Fish Form...and that's about 5 and a half hours in, so I feel I gotta be coming up to the end soonish.)
Not sure if the original creator is still lurking on the forums or whatnot...but eh. Might as well throw my two cents into the fountain.
- The new areas look absolutely GORGEOUS. Especially the "Strange" area of the mod, which really looks like everything in a greenish-lilipad pond scaled up by about a thousand...even the parts of the pond we don't see. The microbe-looking things, the giant dragonflies, the huge tadpoles, the clusters of spores in little nets that make Naija giggle when you break the nets open...all of it looks so cool, and so beautiful. The mines were pretty cool, too, and I loved the attention to detail in the home waters. And the Depths part was equal parts dark/foreboding and bright/alien, especially the room with all the colored pods that had portals that led to different arenas. It reminded me of that alien dimensional thingy from Pacific Rim...which is pretty cool.
- I really liked this mod's approach to combat. In the main game (and in several other mods as well), your combat options for most of the game were Energy form...and that's about it, until you got Dual Form. All the other forms were more-or-less useless in combat, as the average player would just stick to Energy Form in combat scenarios and only switch to Beast/Nature/Sun form when the situation required it. In this mod, though, it's completely inverted: you're not given Energy Form until the tail end of the maze, but you're still given plenty of weapons up until then, like the Urchin Armor, or the Nature Form thorn plants. This forced me to try new things and keep experimenting, employing strategies I'd never use if I had Energy form from the start. Under fire from a Sea Dragon? Sing the Shield Song, dash and grab the beast while wearing the Urchin armor, and ride its back until it dies. Being chased by poisonous worms or relentless nautiluses? Switch to Nature Form, drop a cactus behind you, and laugh as they ram headfirst into the spiky thorns and die. Trapped in a room with lots of projectile-spitting, wall-crawling enemies? Switch to Beast Form and eat and eat and eat and eat...and get ammo for their abilities that you can unleash on the next big tough monster. It's all really rewarding, and helped me develop strategies that I'll bring with me into the main game.
-That said, however, the difficulty felt incredibly frustrating at times. This mainly has to do with how Aquaria handles death; if you die, you just get sent back to the last Save Point, all progress since then lost. And while the Save Points are plentiful in this mod...the tough, murderous enemies are even more plentiful. And all it takes is one mistake, one mistimed dash, one little projectile you never even noticed...and then bam. Game over. I found this incredibly frustrating, even with the generous save points, the generous food supplies, and the generous combat opportunities. And why, why, why, why, why, why, WHY are there giant worms in the beginning area?!? On that note: putting heavy-hitting, quick-acting, can-kill-you-in-a-minute-if-they-get-it enemies in Song Bulbs was just mean.

Overall, though, I liked the Labyrinth Mod. It's a lot more cerebral than other game mods I've played for other games, but I appreciated that. It's gorgeous, engaging, and for the most part, fun. Loved it!