I was very excited to try the Catbird Baby Pikkolo Carrier for this month, as it falls into a unique category of buckle carrier. They often tend to get lumped into Soft Structured Carriers, but there is very little structure. They are more aptly referred to as a "Buckle-Tai", meaning a mei tai that has buckles instead of straps to tie, because in function and fit they are very similar.
The waist buckles in the middle, but has adjustable length on either side of the buckle so it can be situated wherever is most comfortable if you have the length to do so. The shoulder straps also have dual-adjustable buckles, which means you can adjust by pulling in either direction on the straps to tighten. This makes for an easier adjustment when wearing on front, because you don't have to try to pull toward your back. These buckles are also able to unbuckle, which means you have the option to unbuckle the straps and re-buckle them in a crossed manner. Many find that crossing the straps makes for a more comfortable front carry. Speaking of the straps - they are padded with a light memory foam which makes them not at all bulky.
As your baby grows, there is the option of adding a structured waistband to the Pikkolo as an accessory. I did not test this function as we do not have this accessory in our library. It is available for $25 retail, and the carrier retails for $129 from the manufacturer.
I found the carrier to be very comfortable, and I think Ruby approved. She is about 10 months old and 18lbs in the photo, although she is 95% on height, so quite tall for her age.