I failed with multiple slings with my first. We used a Jeep brand version of the Bjorn, which worked okay, but they go rapidly from too small for it to too big. For the second, I bought a Sleepy Wrap. It has more give than a Moby, so you put it on you, then it's easy to pop the baby in and out. Takes a tiny bit of practice at first, but that was by far the best thing I had for my second that I didn't have for my first. The downside is that the fabric is like a double-knit t-shirt -- pretty heavy for wearing here in the summer. I did use it for my newborn in June, but we would both get pretty sweaty it wasn't well air-conditioned (but even so, she went shopping *a lot* in that thing). We then spent a month in cooler temps, and I just wore the wrap all day - popped her in and out as needed. Awesome. So much better for grocery shopping, for example -- no lugging the bucket and the 3-year-old.
Once she was a little older, I ordered a Beco on eBay. Much cheaper than stores. Our Kid2Kid (consignment store) now carries a lot of them, so if you have one nearby, check there. The Beco is fine, but never got as much use as I thought. This kid is just as happy in a stroller. So part of my advice would be to weight on a carrier-type purchase (Bjorn, Ergo, Beco, etc.) until the kid's a little older and you have a good idea of what you need it for. Wraps are cheaper and easier for the newborn phase.