I tried pins once; once!
That's a serious pain in the arske, and my hems still came out all wrinkled and puckered. Honestly when I don't pin I can keep the fabric tighter under the needle and get a nicer looking hem.
For long hems I have taken to using heat'n bond seam tape. I measure, fold, iron, & stitch. I use a 2" piece of seam tape about every foot. This seems to keep things more straight than pins, for me at least.