I have always hemmed my own pants. It's just a straight seam. I even learned how to do the "original hem" on jeans, which is super easy. I don't have a machine, I just do it by hand, and I save the $25 they charge in my area, which adds up when you have a few pairs of pants.
However - I have a feeling an actual tailor might do a better job.
I'm curious what other people think. Do it yourself or pay a pro?