Tip: Layer 3 backgrounds and tides disappear when you hit a message box, so plan your level around that. For example, you can add a sublevel without layer 3 at the start/midpoint, and include your message there.
Visually, this hack is incredibly impressive. The soundtrack is both fitting and functional. I like the level design, although the levels are very lengthy and no cakewalk.
The castle is the only level that feels like it's Mario, drawing on elements from SMB3 and SMW and making it soul-crushingly difficult to beat. It has another path that can be accessed when it rises from the lava to the left of the door to the room with the big eye. However, nothing comes of that side plot at the end of this level. The StarTropics level is full of one-tile-wide platforms and has a very slow pace. It warrants a lot of precision and has a lot of enemies you can't even touch. Spin Jump is disabled in most areas. The chicken level is cute and has secret tunnels, but there's no reward for getting all 30 chickens - you can still exit the level as normal.
What disappointed me even more than the lack of rewards for the incredibly hard levels or incentives to complete the chicken quest was the fact that even though some levels had save prompts, I couldn't get an SRAM telling me I had any more than 0 exits for the SRAM database.
In short, a very hard hack that does everything right except for giving you a sense of satisfaction for the work you put in to conquer it... I feel very bitter about it as a result.