I've actually used duct tape as an emergency method to hem jeans. My husband's jeans were way too long and I needed to get them shortened. I grabbed some duct tape and in about 10 minutes, I had those jeans hemmed!
Regular hemming tape is easy, though. I haven't had to use it too often, but when I have, it has worked very well. I was pleased with the way it held the hems in place. It's good for emergency fixes, too, like if you walk on the hem of a pair of slacks and need to tack the fabric up in a hurry. It can also be good when you're making a garment, to get the hem right before sewing it, since it's less time consuming than basting.