New member here, first post.
I have the OEM rails & cross-bars on a 2015 RAV4 down in Mexico. The rack is used primary for hauling around kayaks, paddleboards, and surfboards - at highway speeds, but for fairly short runs of roughly 25km each way. The heaviest load it sees is when I stack two kayaks on top of each other, with a combined weight of about 125 lb. Although that's above the 100 lb. nameplate capacity, it doesn't seem to be a problem.
I have several concerns with the rack:
1) Cross-bar Placement: as pointed out in previous posts on this thread, it's not possible to mount the front bar all the way forward because the cross-piece isn't long enough to allow it; although this isn't a significant problem, I would prefer to place the bars as far apart as possible, particularly when hauling longer loads such as the 13' tandem kayak
2) Cross-bar Mount: the cross-bars rely solely on a friction fit with the rails to remain in place; this is a woefully inadequate design because a) the rails are slick, so a great deal of pressure / friction is required to ensure a snug fit; and b) the plastic / nylon pieces that you rotate to tighten the mounting bolts aren't strong enough to confidently generate enough pressure; even when the mounts are tightened about as much as you can get away with (for fear of breaking them), it doesn't take much to slide the cross-bars around - e.g., while washing the roof I'll occasionally grab onto a cross-bar to maintain my balance, and it often slides back and forth when I do that; I've seen much better designs that would have been easy & cheap for Toyota to incorporate - e.g. dimples on the inside surface of the rails, with a corresponding protrusion on the mount that would mate with the dimple, allowing for a secure fit without needing to apply excessive pressure
3) Cross-bar Fastening Mechanism: relying on a plastic / nylon piece to tighten the mounting bolts is a pitiful piece of engineering; although slick, quick, and user friendly, it is far from robust; the contact area between the steel 'T' of the mounting hardware, and the plastic tightener, is very small, which places a lot of stress on the plastic when tightening (or loosening) the mount; neither the design nor the plastic itself are up to the task - e.g., if you want to tighten the mount, you need to go one complete 360-degree revolution with the plastic piece so it will snap into place and close (i.e., you can't fine-tune it by doing, say, a 1/4 turn, the way you can with a regular bolt, screw, etc.); any time I want to further tighten the mount, I hold my breath & cross my fingers in the hope that the plastic piece doesn't break
4) Metallurgy: the bolts used to mount the cross-bars and adjust their length should be made of a decent grade of stainless steel, but are not; the bolts on my mounting hardware are corroding, and seizing to the female receiver end with rust; the cross-bar length adjustment bolts are also corroding, to the point that I now need to pound the allen key into the head with a hammer in order to gain enough purchase to loosen them; although I appreciate that not everyone uses their rack in hot/humid/salty environments, I suspect corrosion will eventually be an issue pretty much anywhere (except on the Moon, and to a lesser extent in desert environments); I can't imagine that it would have cost more than a buck or two to use decent stainless steel hardware, but they decided to cheap out instead; I'm planning to replace all of the metal bolts with stainless
5) Locking mechanism: the lock is a complete joke - a 10-yr-old with a screwdriver, or a pair of pliers, or a Swiss army knife could have all four of the mounts unlocked in about two minutes; why did they even bother?
In summary: The rack is easy to install, and looks good. It is best suited to running around town looking 'sporty' (whatever that means), or light duty such as short runs with sports equipment, the occasional load of 2x4s, etc. The rack is not very confidence inspiring in more demanding applications, particularly in harsher environments. If you're planning to use it in such applications, it would be wise to inspect the mounts on a regular basis, and ensure you're using best practices to secure your loads (e.g. tieing down to the rails, not just the cross-bars; running a back-up line over the entire load and looping it through the interior via the rear doors; using bow & stern lines for long items such as canoes). These are good things to do regardless of the rack you may have, but even more important with the OEM rack.