Pros: Eases sore arm muscles. Freedom of movement. Price.
Cons: Difficult to get the munchkin out. Traps heat against body.
I have to admit, I was a bit skeptical when we got our first hot sling,but this product really is a lifesaver. Our little one had colic, and it's just not possible to carry your child in your arms for 18 hours a day. My wife and I both had sore arms, our backs were aching, and our midwives suggested a sling. This has got to be the best money ever spent!
The sling lets you carry your child in several different positions, thus freeing up your hands to actually make a bottle, do a load of laundry, etc. It keeps the little one nestled close enough to have that reassuring parental heartbeat which helps lull them to sleep, even through some of the smaller colic bouts.
The best part is that you can use the sling to carry an infant, which is ill advised with some of the other carriers (i.e. baby bjorn.) The sling offers support to the entire back, neck, and head of your baby. The bjorn style carriers require the little one to have strong enough neck and back muscles to keep their head from lolling back and forth.
Another feature that I appreciated was that they offer it in some daddy-friendly colors as well. I know it isn't the most masculine thing to have a baby strapped to your chest, but when we were watching the game with the little one sleeping and me able to hold a beer in one hand & snack with the other, I got the last laugh.
These things really are a great little tool. The only down side is that they trap heat something wicked. If your little one is a hot-box like ours, be prepared to roast if you're "wearing" them for extended periods. Of course, if you were carrying them for the same time you'd be just as hot & have sore muscles to boot. Also, the UV mesh variant is thinner, allowing for air to circulate better, but it's also pretty scratchy. Our little one didn't dig it for the first 4 months or so.