I’m pretty sure I’m the only one here playing this co-op but I think it’s balanced well, depending on your partner.
HP scales so you’ve got to both be hitting bosses and enemies for longer to move on (seriously, those tree trunk enemies on Treetop Trouble are super tanky co-op). This means that if one of you dies, you’ve got more work to do on your own. You can revive each other if you’re quick enough but it’s sometimes impossible to reach your partner’s ghost in time without killing yourself. You can also die if you fall off the screen at the bottom whereas solo the screen simply scrolls down.
My girlfriend is doing amazingly well but she’s not as dexterous as me so when things get busy (with two of you on screen shooting, it’s a lot busier by default) she can sometimes struggle. That said, she’s carried us over the finish line a few times now which has been glorious.
We’ve just got to world 2 and reached the final stages of Baroness von Bon Bon on Regular. I was convinced that Mario + Rabbids’ world 3 boss wouldn’t be bettered this year but I think Cuphead has it in the bag quite comfortably at this point. So creative and exciting.