Pros: Can see baby, comfortable, one arm totally free, baby gets to interact, easy to use.
Cons: You're got one fully mobile arm and the other is like a vestigial T-Rex arm.
I own four baby carriers--one front only carrier (the EuroRider), one back/front carrier (the (Ergo Baby Carrier), one body sling (the Maya Wrap), and this one. I've used all extensively with the exception of the Maya Wrap, which confounded me. They all have their purposes, but the hip hammock is my weapon of choice for around-the-town urban assault. It places your baby nestled under your arm where you can protect her and check up on her, and on your hip where she's still comfortable to carry. Putting the baby in and taking her out are easy so you don't have to fear dropping your baby. When you're not using it, the hip hammock rolls up and ties around your waist.
The design of the Hip Hammock is very simple. One strap snaps securely around your waist and another strap goes over your head and one arm to rest against your neck and across your body. Both straps are very durable nylon and adjustable. The strap adjuster has never slipped from where I put it, which is something I feel is very important while carting around a baby. The strap that rests against your neck has some thick padding to make it comfortable resting there, when you get it out of place you'll know it! There's a little clip on the neck strap for you to hang a baby toy to entertain the tot. I snap on a little baby key ring, but when I go into the store I often snap my real car keys as well so they're handy when we're trying to leave. The Hip Hammock comes in a right-handed and a left-handed version, though either can be used on either hip. The snaps and adjusters are just more easy to use if you're wearing the right-handed version on the left hip, and vice versa.
The hip hammock is rated for kids 15-35 lbs. Your baby should be able to hold his own head steady while you cart him around on your hip before you start using this carrier. Most of the weight is carried on your hip, though there is some pull on your neck as well. My baby is 6 1/2 months old now and 19 lbs. We've been using the Hip Hammock for over two months. I'm comfortable wearing the baby for a good hour at a time cruising around the store. Much more than that and my left side, and right neck starts to ache. Switching to the other hip before that happens helps to alleviate this since you use all the muscles on the opposite side.
I use the hip hammock primarily for initial chores in the morning and errands around town. She's so close to my body that the added weight doesn't put undo strain on my back and joints while I'm still stiff first thing in the morning. Since she's at my side I can twist away a little and prevent little fingers from grabbing at my hot coffee mug as I'm trying to wake up. Because she's under my arm, I can slip on my oversized gortex field jacket (picked up for a song at the returns room at Cabela's--woo hoo!) to keep us both warm while I tromp around the yard. (Something that I can't do with the back carrier.) She's so close that the body heat helps, too. I can bend to pick up heavy items (up to 40 lb bags of feed and 20+ lb frozen turkeys) with some difficulty, due both to having a baby strapped to your hip and because you're effectively one-armed. I try to time the heavy lifting for when she's down for a nap. But it's still possible to do if you're strong and careful.
Errands around town are really easy with this also. When I go to the store or take her to baby swim lessons, it's an easy thing to slip her out of the baby seat and gently lower her from my shoulder into the baby carrier. When I want to take her out, I just hold her to my body and pop the top strap, then lift her free. There's no complex balancing motions for you to fear dropping your precious baby on the concrete of the store parking lot, and you put her in and take her out unassisted. With her against my side, I can easily navigate doors while carrying a gym bag or canvas shopping bag. You can readily push a shopping cart as well, though mostly one-handed, which will get challenging if you heavily load it with groceries, People are mostly pretty eager to help a lady with an adorable baby strapped to her waist though, so I've never run into any insurmountable physical challenges.
Of all the carriers I've used, this carrier was definitely the easiest to begin using. With all the others I had some degree of consternation, frustration, and unsuccessful attempts before I got used to them. This one was out of the box and in use within 10 minutes of taking it out of the mailbox. Baby took to it right away as well, since she can see where we're going and interact. When she sees something that strikes her interest (like any cat!) she leans way forward. When we meet people she can check them out from her safe and secure perch on mommy's hip. She can flash smiles at them, bury her face against mommy, or if she wants to explore more, she'll wave her arm to try to touch the person's face. It's a lot of fun for all. I can see her face and know if she's starting to get sleepy or is just taking in all the sights. If she falls asleep in the carrier I make sure she's good and asleep, then hold her snug, pop the top buckle, quietly lower the top strap (it's got that clanky baby toy attached) and lay her gently on the bed. I can usually manage not to make her wake up.
One note though--the original Hip Hammock design has been purchased by Playtex. My experience is with the original Hip Hammock--Playtex is now marketing an original and deluxe model.