We are looking at these too and DH has heard quite a few negative reviews...
I think we will probably still go for it though, as I'm not sure that we'll need the toddler seat for a long period of time as DD will be 2.5 when new bubs comes and probably I will use a sling when the newie is tiny (DD HATED the stroller until she was around 3 mo... Not sure if this one will be the same, but I'm prepared for the eventuality.) I don't want to buy a tandem or side-by-side only to find I hardly ever have two kids in it, KWIM?
Probably this doesn't help you at all, but these are just my thoughts atm! I don't think the other joggers with detatchable toddler seats are as good from the limited research I have done.