yes thats good for incrementation but i think the way you can type = in attribute editor is better, although it makes a expression but that would be fine you can always detach it. As such you cat really do any complex maths.
As such it would be sane that it would just compute the thing typed in. I mean if i typed 2*5+sind(20) how hard should it be. This would fix any need for units too (which off course isn't a problem if you happen to work with SI units because its no harder to increment 3 meters in a cm system as its in a m base unit valued system. Now if we only could make 100 fraction as easily a 60
)