I got the Seat bars with my car when I bought it. They guy who owned it previously had them for a roof box.
I spent quite a lot of time reseaching roof bars and cycle carriers recently.
I don't know if it is a specific 'aero' bar thing or not, but I would always look for bars that have slots in the top. It makes attaching things much easier as most things you want to put on the roof have fitments that just slide down these slots. The Seat bars have this. They use a specially shaped fastener to tighten them up too, so unless you have the supplied tool you can't get them off the roof.
The cheaper cycle carriers don't have the ability to use the slots I just mentioned (unless you buy an adaptor from the manufacturer) and this means that they take longer to mount to the bars.
In the end I was looking for a cycle carrier that was quick to mount/dismount and held my bike securely/was easy to attach my bike to and was lockable.
I considered the Thule Proride591 (or something like that) and then discovered an Atera carrier that was very similar called the Giro AF. I liked the fact that the arm that holds the downtube of the bike attaches to the carrier on both sides at the bottom so is more of an A frame than the single arm of the Thule. I think the Atera won an AutoExpress test a while back and when i phoned The RoofBox Company they recommended this one as being better than the Thule.
I actually bought if from The Roofbox Company (
www.roofbox.co.uk) and am well pleased with it (and the service I receivced from them).
The bars and carrier now take me about 10mins max to mount/dismount and I have only done it twice so this will probably get faster. When mounting the bars I put a tea towel on the opposite side of the car to rest the other side on prior to securing. The cycle carrier uses quick release style clamps to grip the bars and one of these has a lock in it to lock it to the roof bars. Once the bike securing arm is in place that is also locked so the bike can't be removed.
I am not sure I follow DaveP's comment about aero bars making it a faff with bike racks and losing the easy way of adjusting Atera racks?? Could you clarify?
My only complaint is that the Atera instructions weren't crystal clear and getting it constructed right is obviously of paramount importance!