We usually use washables, but disposables when out (& ds's childminder will have no truck with washables).
Recently we've acquired a compost bin for the garden, which comes with a leaflet sternly telling you what NOT to bung in it, including disposables - but I've seen mention on another thread of composting Nature Boy & Girl nappies?
Can you just chuck them in the composter, or do you need a wormery? & if so, what's the difference? We now have dd so we'd probably be looking at up to a dozen disposables/week (ie. the one ds wears home from CM 4 days a week + ones worn by both kids when out for a longish period).