I got a Nature Baby ring sling (note: NOT nature sway, which I think from some threads some people didn't like).
I love, love, love my ring sling. I am trialling different back carriers also now, but I wouldn't give up my ring sling -- it's just so easy to get DS in and out of that we use it all the time.
The one I have has a padded edge on it, which I'm not sure whether they all do, but it's good -- it means it doesn't cut into DS's legs when he's in a hip carry.
A tip -- it took me a while to figure out how to use it comfortably -- you've really got to spread the fabric across your back and shoulder -- spread it out as far as you can, otherwise the weight goes on your neck.