It's the only way to go since we only take carry ons with us when we fly (we gate check the car seat or bring it on board if there's an extra seat in the row). And since we now travel with an infant, I pack for two- in the same carry on that I used to pack for one- and I'm always looking for ideas to pack more efficiently. Here's the top three that I've found:
(1) pack your baby's clothes by the day in ziplock bags.
This is great because not only does it keep your carry on bag neat and organized (like if you get lucky and TSA wants to search your bag) but the air can be squished out of the ziplock bag (you know what I mean) to create even more room in your carry on. I liked the idea so much that I even did it with gallon sized bags for my clothes.
(2) Roll your diapers tight. In the past, I usually packed just a few for the trip over and then bought more once we got to the place we were going. But since we recently received some diapers that were originally part of a diaper cake, I kept them rolled up and stuck them down the bag wherever there was a pocket of space. This worked great because they stay rolled tight and didn't get smashed or loose their shape at the bottom of the bag.
Which left us with feeding while on the flight. (3) And this is my favorite: the bazooka of all baby spoons, aka the Boon Squirt! 
Before we leave for the airport, I pour a jar of baby food into the handle of the spoon (ours is a bright pink) and wha-la! A no mess, easy handling feeding ready to go when it was time. Which also works great because the spoon never needs to leave the baby's mouth- just a continuous squirt (which is a bonus for us since Savannah gets impatient when we don't spoon fast enough for her!)
In the end, I was able to pack into one carry on (that fit under the seat in front):
- 4 days of outfits (including Sunday dresses & pajamas) for both Savannah and I
- 4 days worth of diapers & wipes
- A pair of dress shoes for me
- Shampoo/ Conditioner/ Shower gel/ make up
- My flat iron
- A church shirt for Brant (who was meeting us down in Texas after his trip)
- My bulky SLR camera
- A light weight baby blanket plus baby sleep sack
- A (small) diaper bag with toys and baby food that also doubled as a purse
And I had room to spare.
Time for take off!
P.S. Look for Texas pictures on Savannah's blog- they are all mainly of her!
