I have created a few worlds with high random tick speed, and the result is low TPS. 
Here are some examples of what I have experienced:

• Potions won't give you effects, or its takes a few minutes for the potion to work
• Mining blocks then placing the block in that spot will switch back to the block you mined, making this a nightmare for people in survival with high tick speeds
• Using repeating command blocks with a delay of 0 ticks, my guess is the ticks per second is 2.2