I made one and it came out great. And I don't consider myself to be great at sewing. I used the one at http://www.ida.net/users/stace/sling.html
Personally I adjusted my pattern a little, my fabric was ugly on one side so instead of cutting it in two on the width I sewed it together wrong sides facing and turned it. Then followed the directions for the french seam. I love having a sling that was the exact color i wanted and was super cheap to make since I used a simple cotton pring I found on sale.
Good luck with your project.
Personally My next goal is to make a Mei Tai for my now toddler.