HI,
I have had a Mamas and Papas double side-by-side buggy for 31/2 years. Initially it was for twins, but ended up being for one new baby and an 18 month old. I bought it because it fitted through ordinary doors, even though it was a side-by-side buggy. I tried the front to back style, but as I am 5' 2", I was unable to manoevre it very well, especially with the 18 month old at the front. It lies right down so is suitable from birth, it is light, and designed to stand upright on its own.
I have thin children which have not been cramped up in it, but I can imagine larger children, especially as they got older would find it a tight squeeze. I have definately had my money's worth out of it, but it wouldn't be for everybody.