This is a no-brainer that should make its way ASAP into 13.
Provide users with a way of tweaking their brush settings and then SAVING OVER an existing brush preset, rather than having to create a new one.
The brush preset system that has been in place since 5 is a broken user experience. You always create a "throwaway" brush (tip) when you Define Brush Preset, and then you customize its settings and create a New Brush. Then, if you don't like those settings and want to improve them, you are stuck having to create yet another brush preset, and eventually deleting the others.
Come on guys, we need something just a little more polished. It's been over ten years now. Fix some basic stuff before launching into crazy new directions like 3D.
For the most intuitive user experience, the workflow should be revised.
Creating brushes should be a two-step process:
1. create a "brush tip" - these are the sampled pixels only, with no Brush configuration data attached
2. create a "brush" - by selecting a brush tip and then setting your options.
If you then want to edit an existing preset and save over it, why not present us with familiar options like Save and Save As? Put a little "save" icon and a "clone" icon in the Brushes palette. Let us know when we're editing an existing brush preset, and put the title of the brush preset in the palette. Basic basic stuff.