Is this a good random routine? [Taken from pokecrystal]

Random::
    push bc

    ld a, [rDIV]
    ld b, a
    ld a, [RandomAdd]
    adc b
    ld [RandomAdd], a

    ld a, [rDIV]
    ld b, a
    ld a, [RandomSub]
    sbc b
    ld [RandomSub], a

    pop bc
    ret