Hwedhlor - great topic. This is one of those important details that often gets overlooked by many manufacturers.
Common practice is thin-wall ABS keytops, with acrylic ink legends. The texture is usually very smooth.
Some keys have dye sublimation printing, to penetrate more into the plastic. (It still wears out though).
Some have painted surfaces, with laser etched areas (for backlighting). The black keys of a MacBook Pro are done this way. They're actually translucent white ABS plastic, painted black and then burned off with a laser to let the white illuminated plastic show through. This is good because the white legend will not wear through, but the foible is that the black paint surrounding the legend eventually wears through, and then the legend outline becomes indistinct. The MacBook keys are also a very smooth finish, which means the black paint is in a thin layer.
We took some different approaches from convention in order to increase strength and durability,
We start with a higher grade polymer. Polycarbonate costs 2-3 times more than ABS, but it has superior strength, fracture resistance, and durability.
Because TextBlade has innovative frameless keys, we wanted them to be much stronger to survive multiple drops. The keytops are molded with 40% thicker plastic, in super shock-resistant polycarbonate.
The base resin is clear PC that has been pigmented throughout its thickness, so the key color is not painted, but instead solid plastic, and has a color depth depth more akin to clear coated car finishes.. The color will not wear out.
The legends are printed in premium grade metallic polyurethane paints (similar to super tough automobile exterior finish paints), which have very high bond strength so they cannot flake off. These legends are double-printed for an extra thick coating that can withstand significant abuse.
The surface finish of the keytops is in a matte velvet texture, that produces a satiny visual sheen, and luxurious surface feel. More important, the deeper texture provides microwells to hold the metallic urethane paint, safely below the protective peaks of molded polycarbonate.
The result is an incredibly strong legend that's built for years of heavy use. It is the equal of the MagLever spring-less butterfly technology, which also has no contacts to wear out.
When there are 8 ultra smart multitouch keys instead of 80 rubber buttons, we can afford to lavish more expensive materials and processes on them to create a much more refined feel, and much longer life. The key surfaces will look new much longer than conventional keys.