I finished it. It took about 13 hours with 75% completion and a bit over 3000 deaths. I don't think I will even bother getting 100%.
The level design is good, the mechanics are solid, however the aesthetic just kind of bugs me. I know gloomy, depressing, worlds are a trademark of Edmund games, however I liked Super Meat Boy a lot because it had a cheery 90s aesthetic. I also liked SMB more due to having a map and not having to dredge through entire worlds to get to secret levels.
If you're thirsty for 2D platformers, you'll have a good time. Otherwise you can wait for a sale or give it a pass entirely.
spoiler (click to show/hide)
Also the final challenge is going through the last world in reverse; with a fucking time limit. Fuck that shit.