R.S.
I have the older model of the sit and stand and LOVE it! I am due with our 3rd child in May and am going to buy the newer version of the sit and stand. It allowed our oldest one the freedom to get in and out whenever she was tired. The ONLY reason I did not like it was when we were going to be out for a while, as there was no where for my daughter to lay down if she had fallen asleep. But for errands, walks, zoo, etc. we used the sit and stand! Hope that helps!
Also I want to add, that my daughter is big for her age. She is on the scales of a 6 year old at 4. As far as the age and weight, they hold up great!!