I used a Baby Bjorn for my 2 boys (3 and 5 now) and loved it. But, my boys were light and I only used it until they were about a year old. DSIS has twin boys (8 mos) and they swear by the new Baby Bjorn that has back support (which is even more expensive!).
However, I'm pregnant with my 3rd and am really interested in slings. I like the thought of breastfeeding the baby in there and being able to walk around. Also, since this is my third, we are always going to be on the go and I think this will be the easiest way to get around. I have already bought an adjustable fleece pouch from Kangaroo Korner and I can't wait to use it. If we (me and the baby) like it, I will probably look at getting a solarveil Hotsling for the summer (I'm due in March). DH will still use the Baby Bjorn because the slings are sized and probably won't look very "manly" on him.
I'd love to hear what other people are using, too. It's a tough decision. I wish you could find them in stores easier so that you can try them out.