i also bought babybjorn-synergy. most of my friends use this and strongly recommend. before i also wanna to buy combi 4 in 1. but finally bought babybjorn-synergy due to my friends has bought combi and sling and find both are not so good as babybjorn.
i used babybjorn when my daugther just 1 month , very good , easy to use, MAIN POINT is protect baby back side really really good ! this is very important than all the things