Yeah the slow motion prevents me from actually enjoying this game. It makes it more of a grind and a "hurry up already" than a "oh look at this cool thing I did." Mostly because slamming into a brick wall isn't really that cool.
Beat it once regularly, then read through the comments and saw someone say a level 5 chain turret sells for more than the upgrade cost. Turns out that's true for ALL the guns. So I played through again and bought and sold a bunch of stuff until I ended up with 3 level 5 lasers on every elevator. I barely saw the monsters step on to the floor.
 "Bloons Monkey City"){kind=icon}
 "Bloons TD 5"){kind=icon}
 "Earn to Die 2012: Part 2"){kind=icon}
 "The Next Floor"){kind=icon}
 "Trollface Launch"){kind=icon}