Total playtime: 5 hours, 22 minutes
All 86 exits unlocked.
The level design was very consistent, each world had its own specific theme and Gamma V did a great job sticking to that given theme. Seeing as there is no time limit in any level, the player gets the chance to explore the level without any issues.
The Star Coins had an interesting gimmick, seeing as some levels with secret exits could give you a key upon collecting all five, unfortunately though, some levels contain sprite variants of the Star Coins, which can be exploited by re-entering the level with pipes, causing the sprite coins to re-appear. This exploit can give you multiple 1-ups and even multiple keys if the level has this gimmick enabled. 
At times, it felt like I was playing an actual Mario game, there were a few throwbacks here and there to classic Mario titles, some of the world's themes were very recognizable from official Mario titles, and some of them were never before seen.
The overworld looked very clean, simple and gave you a basic idea of what to expect for each world. I don't really have anything to add to that, apart from a few nitpicks. (Hover over the links for details)  
I would also like to point out that the music on Lunaria is slightly broken for the first second, this is most likely either an old song that doesn't work well with accurate emulators, or the port wasn't done correctly.
When it comes to aesthetics, the levels were very well put together. There's always something to look at on every part of the stage, and seeing as your screen is cleared from a status bar most of the time, you were able to admire the level design even more. The graphics were very well made and fit really well inside of a Mario title.
The songs used in this hack were well chosen, some of them didn't really fit in a few levels, but it's nothing too bad, the songs were quite pleasant to listen to. Mushroom Plains 3 has an issue with its music though, and that is that the sound effects being played will come out kind of broken. (Like if you would be using ZSNES)
The hack starts off easy, but gets progressively harder as the levels go on. It stays fair, and could easily be played by anyone who likes to play Mario games casually. The final boss may be a tad bit too hard, though, as a lot of stuff is happening at once, the projectiles that the boss fires also goes really fast, leaving you to get hurt because you don't expect it right away.
Apart from all the things previously mentioned above, there are still a few bugs that were overlooked. Some of them being minor, while others could be a little bit confusing.
If Mario holds an item and turns around, his head dissapears.
Pipe City 2: These upside-down Munchers don't hurt you.
City Secret: Jumping up here to the right side of the screen causes Mario to teleport inside of the pipe on the left, causing him to instantly die.
Winter Fortress: This ice block sprite may dissapear due to sprite limitations, walking back and forth will make it re-appear, though.
Metal Kingdom 3: Continuously walking to the right will shove you inside of the wall because of the conveyor belt, causing you to instantly die.
Lunaria 3: These spikes will behave like coins once you press the silver P-Switch that's active in the level. Seems to be lacking ExAnimation.
Every Lunaria level: There's a weird side-effect to the modified gravity. Either scrolling the camera using L or R, or pausing and unpausing the game, will force Mario to jump either low or very high, automatically.
One minor nitpick
Tiki Island 3: The layer 3 water used is fixed in place, meaning that the water never scrolls with the actual level.
Despite all of the flaws mentioned above, the hack is still very solid, fun, playable, and most importantly; beatable.
Therefore, this hack gets a feature