Double buggy days

When my sister had her son five years ago eighteen months after her daughter she found her pram choices to be quite limited. Now, it seems that every pram has a toddler option. I really like the Phil and Teds one and by the traffic on Essential Baby, so does a lot of other people.
Do you think the one underneath would be battered by the road? When I was first pregnant in 2003 I saw this and wondered how you could carry the child so close to the ground, but I've since seen it in the flesh and it looks quite cool. That choice survey, however, from memory said the harness had some safety problems. Not that I will need a double pram soon, but you know how obsessed I am!