yup, the GDI is handly as a secondary drive pedal. i use it to shape my tone properly on amps with distict default sounds... for example, i want a fat chugging sound but i'm given a bright marshal... i just dail in some mild calif mesa boogie setttings on the GDI to fix this, but use my main randolfied ds-1 to push it to distortion...
if u are looking for a particular distortion, maybe u would like to get a main distortion pedal first. but if u have no preference and want versitality, get the GDI-21