I have used the Yakima rack for 6 years and two cars. I have driven over 8000 miles with two kayaks on top, and without major transport problems. In one instance, I demolished the front of my car coming back from Canada in a collision, without the racks and boats shifting more than perhaps three inches.
Having said that, I will be trying a different manufacturer this time. The limitations of the Yakima system are detailed below. They may be faults of all of these sorts of racks; I have not yet used a competitor.
Plastic fairings on towers are required to hold the system together, but they have a tendency to fall apart.
The tower clamps utilize a plastic lever to lock the cams. I broke two of these over the years, loading up in cold weather prior to driving to Florida.
Silicon pads under feet are poorly secured, I lost several over the years.
Kayak hull cradles had several hardware problems, too numerous to report here
Strap clips on Hully Rollers are not structurally attached to rollers, I lost several.
Bolts that clamp cross bars were low grade steel (my opinion), they had a tendency to strip prior to gripping securely. Eventually, I had to drill and thru-bolt one of them.