i hated the Kelty Kangaroo. if you have a bit of a spare tire (love handles, fat) around your waist, the kangaroo might work for you. but the design is such that if your waist is straight (or tapered, as mine is) then the belt is useless and the baby's weight just hangs off your shoulders. i suffered a lot of pain before i finally got rid of the Kangaroo.
for babies unable to sit up, we switched to slings. they are not perfect but they are a danged sight better than the Kelty Kangaroo, especially for in-camp time. they are also more versatile (multi-use) and the baby can be carried more than one way. for crawlers & toddlers they are still a useful item to bring along – close containment! There are many varieties of slings available; we've mainly used simple ring slings. most of the commercially available slings are made from cotton. (blatant self-promotion: if you decide you'd like to try a sling but don't want a cotton one, I sew and sell baby slings and could make you one in a synthetic fabric. fleece slings are nice for cold weather.)
i can't recommend the Kelty carriers. they tend to run on the heavy side and are mostly overbuilt. we own two carriers – an REI Piggyback and a Madden Caravan (which is now the Sherpani Rumba). my husband loves the Piggyback but hates the Caravan, and i am the exact opposite. IMHO, the belt on the Piggyback sucks, and my husband's back is too long for the Caravan. there is a review here on BPL of a Sherpani carrier and i think it was positive.
edit – there is very little storage capacity on the REI Piggyback, but we got around that by tying stuff sacks into the lower half of the frame. my Caravan has an outstanding storage area built into the lower half of the frame. some carriers have a detachable day-pack type thing that hangs on the back, but unless you fill them with very light items they are worse than useless and pull the back backwards. we mostly take these off. older models will not have bladder pockets (if you use a bladder).