I have a Tyion sling and its really good. DD is almost 7 months, and a little puddingly (sounds nicer than a fatty! ) and I use it daily. And its cute too, the logo has a mum & baby on it. Google "tyion sling" if you want to have a look-see.

I am going to put my Baby Bjorn on ebay (and rave about it in my ad, of course! ) because it really is an attrocious peice of back torture!

Suse is the baby wearing guru though & there are heaps of threads in the baby wearing section where she goes through the pros & cons of just about every sling on the market. I'm sure you'll find something that suits and doesn't hurt your back.