I have adjustables that work by both coming down to a trapeze adjuster type cleat at the base of the mast.
We tend to use them as part of our "gear" changes.
When we beast on the cunno to de-power the uppers go slack, then we can pull on a bit more to keep the top of the mast supported, then let off a bit of cunno to tension them up again.
Also, if it turns out to be horribly gusty (3rd day at Weston) we can let some off to give us a bit more response from the top of the rig.
In short, we have adjusters, we use them and we like them.