You know, we got our DS's first haircut at Main Street, on his 2nd birthday, and he really didn't like it. I had read about how the barbers were "specialists" but I didn't think the guy who did ours was anything special. I had to hold him in my lap and he cried.
But he needed that haircut --- until then, I cut his hair while he slept and night and you can imagine how it turned out all the time.
Once he hit 2 1/2, my husband took him to his same barber, and now my DS isn't fazed at all with the clippers giving him a little buzz cut. Doesn't care.
So I would recommend you wait until 2 1/2, but that is only based on one mom's experience!