Don't require track mattes to be above the layer it modifies (and also allow re-use)

Some sort of a node-based approach would be great here, even as I know full well that AE is a layer based compositing system. It would be nice for stuff like matts.
I end up duping the Matt layer, and setting up expression links from the 'Master' mask keyframes to all the dupes in dupe layers, effectively 'cloning' the matt layer, so if changes are made, they roll out to the dupes.

Set matte is great for shape layers. It's not a workable solution for image layers though.

Size differences tend to put the matte where I don't expect or want it, and transformations are ignored. Only track mattes do what I need for image layers, but at the expense of needing to layer them in the expected order and often making a bunch of duplicates.

We don't need set matte if the trackmatte did what Micah said, it was the way Combustion did it and I was always mistified about why AE couldn't do it like that.

Use the Set Matte effect! The only drawback to it is that if you're using it on footage layers or solids that don't have the same dimensions, it doesn't work as expected. Still extremely useful for vector/shape/text layers though.

Oh please! I've been saying this for years. This would be soo handy!