I have just taken the McKinsey Solve recently and I'd like to share my experience. In the ecosystem game, I managed to identify 7 out of 8 species, the 8th species resulted in an animal with 0. The difficulty was that the elevation I chose made it hard to establish a viable chain with 8. I should have chosen a different elevation at the time, but I didn't have enough time to replenish all of the animals again. 

In the second part, I did the RedRock Study, which turned out to be more manageable than I anticipated except for the tricky aspect of time management.It includes 2 main parts but each phase is divided into many different parts so balancing the time for each part is very important. I spent too long on the initial phase, leaving me with just 10 minutes for the subsequent part. I relied solely on free resources for practice, I realized the test's nature was distinct from anything I'd encountered previously. Some people report that it was kind of like GMAT. I personally found it different as it focuses more on calculations than interpretation.

That's my opinion, BTW, does anyone know how long it will take to receive the results email?