I finished the entire thing with exactly 250 deaths! All 20 levels!
I think the mechanic is very well realized and there's a lot of things that can be done with it. Lots of different enemy types for a jam and the change in speed and jumping power for the character depending on if you have your friend held or not.
I think one of the major weaknesses of the game is how long re-attempts take because of how slow you can be. There's also the fact that menial events such as climbing ledges can be lethal and/or run ending.