I had the boys microchipped last week. Scooter was not fazed in the least, the needle that they inject the microchip with is quite large, and he never made a peep. As soon as he was done he jumped down from the vet's table and started poking around.
Clyde was a different story. He had to be held down by 3 people. And he let out the most pitiful cry. I had to keep reminding myself that it was for his own good.