I had to change things up a few times with my DS as well. I have the K'tan and love it, although it can be difficult to size. I used it a few times when DS was an infant, and it was awesome...but once I lost a bit of baby weight, it was a little too big, and DS stopped liking it. I did use the Bjorn for a little while, but won't this time because of the hip dangling thing...although it did allow me to pack up our apartment when we moved when DS was 3 months old. I like the idea of wraps, but I am super intimidated by all of the wrapping...that's why I loved the Ktan - it was pretty straight forward and easy to use. Once we moved, DS fell out of favor with the carriers for a little while, and then we went back to it at about 6 months old. At that point it was a life saver...we were back with the Ktan, since DS had grown so big that the sizing thing was balanced out (he filled out where I didn't). I used the Ktan for all of our outings - walks, but especially shopping. He did NOT like the stroller. Once DS was about 18 months old, he became much more interested in the stroller, and we would take walks into town to the playground, and he loved being able to watch the cars go by...but if we were going for a hike, he was in the Boba (we got the Boba (a SSC) once DS turned 9 months or so because he was just getting too heavy and going through a nap funk, so I wold throw him on my back and do chores while he slept). At 2, he would rather walk or push his own carriage.
This time around, I may buy another ktan in a smaller size, I also found a cupon for a seven slings infant sling so i got that for free, i scored a used mei tie for cheap, and we still have the boba and the larger size k'tan...i think i may try making my own wrap though - it seems easy enough to buy the fabric, and this time I will experiment with it before LO gets too wiggly. Around here there is a Babywearing Yahoo group that meets once per month and I went with DS to try out a few different carriers (they let you rent them for a month for a refundable deposit) and you can usually buy some used carriers for pretty cheap too...I love the "try it before you buy it" thing because you never know what your baby will like! i would look for something like this in your area.
All in all we did use the stroller when DS was around one and a half, when he was too interested in what was going on around him to be held so close to me in the carrier, but too little to walk on his own...and usually just for leisure.