I have a Natures Sway sling that I got from TM for about $50. I think they're around $65 in the shops. It was an absolute godsend when Em was really small, as I could tote her around the shops and she'd fall asleep in it. We didn't use it for a couple of months when she was about 5-8 months old, as her butt was too small to "sit" in it the way they're supposed to, but now that she's bigger she can ride around in it on my hip. She's just like a little monkey, clinging to her mama!
What I like about it is that it's got a padded strap to go over your shoulder, which makes it more comfortable. The material is sturdy and easily washed, and it clips and unclips easily. It's portable -- I can scrunch it down and shove it in my handbag really easily. It's also adjustable, if you're "well endowed" like me and need it to be a bit looser! And we got it in a neutral tan shade, so my DH could also use it.
What I didn't like about it was that there's a lot of fabric to the sling part, and when Em was really small, she could get "lost" in it and I kept having to fold the fabric back to make sure she was okay! But it may just be first-time motherly paranoia... She was always fine! And now that she's bigger, having more fabric is really useful.