Most people who have had Microblading have stated that the discomfort is no greater than that of getting a regular tattoo. Many even report that their artist used a numbing gel which totally eliminated the discomfort. They claimed that all that was felt was the pressure of the instruments on their skin.
If you are worried about experiencing discomfort while having Microblading done, speak with your eyebrow artist and see what steps they take to eliminate or prevent discomfort.