When on tour I use it, but for range days/small exercises I hate the ******* thing, and avoid it wherever possible. Trying to get a natural firing position during an APWT is near impossible when you keep having to clip/unclip it for prone, kneeling unsupported, etc. I've found my range days to be that bit more relaxed without it.
I found that the carrying (clipped) length was just right for locking the weapon into my shoulder for kneeling/standing unsupported position. However, alternating between the varying positions was a nause, so I ditched the sling altogether. It's purely a comfort thing; my shooting hasn't been affected at all since I ditched it.