First I think you should ignore another post on here. A 3 yr old has a mind of his own, I would know, I have one and just had a baby on the 3rd of this month.
Last year my husband and I saw a Sit-N-Stand at the zoo and thought it was the best thing ever! That mother was using it for 3 children!
As a Christmas present my mother bought us a Baby Trend Sit-n-Stand stroller. This has been the best thing to have!! So far we have taken it to several malls and to a museum.
Now you are right, the seat does have to recline to accomodate the infant carrier, but it is not to far back that my 3 (soon to be 4) yr old son cannot sit there. He sits there or sometimes prefers to stand so he can see better, especially at museums. The stroller has 2 buckles on the back part, one to buckle the child if he is sitting and another that goes on behind him while he stands. It's a great safety feature.
Also, just as an FYI, to be such a long stroller, it sure moves smooth and easy and folds up to be about the same size as a regular travel system. The only thing is that the basket is a bit difficult to reach, for instance we have to put the diaper bag in sideways or it wouldn't fit. Other than that it is great.
I hope this helps you decide, I absolutely love mine and don't know what I would do without it!
Good Luck