The half step method is used in pitch-class set theory in atonal music but unless you're into that in a big way most people get by with 1, b3, 5 rather than 0,3,7.

I guess the emphasis in modernist music is on the chromatic scale rather than diatonic reference points and the method allows you to see the relative size of intervals measured by a common unit from a given tonic note.

In Schenker's view this allows you to make a connection between C, Eb G and C E G since the distance in half steps between E and G is equal to that of C and Eb, while both chords end in 7 half steps (G).
That comes more into it's own when you consider sets like C Db F# and C F F# which are linked in the same way. Its like saying a b2nd followed by a p4th is in the same family as a P4th followed by a b2nd; it's just in the reverse order.


Alan