I'm enjoying the large magnet range, and the fact that items don't disappear over time. Don't have to scramble for pickups while dodging arrows and mushrooms. I would like the option to upgrade between levels though. Still a 5/5 as is for me.
Idea: When multiple boards of one type are maxed out, could they condense into one square and still give the same amount of auto DPS? This could save screen space and memory. If you want to actively play any maxed out board, it really doesn't matter which one you go for.
If you don't kill the things that the arrow points to, then the boss doesn't come and they keep spawning. Kill a few and go away for a minute a few times to rack up easy moneys.