The difficulty curve could use some work - I've never been able to make it past level 2 without losing one of my peonies, but once you have flax it's really easy to earn money and just cover the screen with gnomes.
The fisherman is a waste of money - you have to pay to unlock it AND pay to put it down, and it's not like bugs actually attack on the water so you have to choose between collecting gold or slowing bugs.
I love the pheromones mechanic - it's a really unique take on the tower defense genre!