I actually prefer being able to freely rotate the sheath around..
I started out yesterday wearing the AR vertical, but after about 2 hours the G10 scales had chewed up my side quite a bit, so I started angling the AR forward, and then rotating back to horizontal for the draw.
This setup works perfectly for me.
Kudos to Strider on the design of the kydex sheath, it's really quite ingenious. Perfect fit with not rattle, and very secure.