There are obviously a lot of factors involved in good vs. bad directions and voice commands, but while I agree Apple has a way to go interpreting requests to specific addresses and guessing exactly what you meant in less-obvious cases, Siri has consistently done extremely well giving directions to specific chains or common types of store on request.
That is, if I ask "Give me directions to the nearest Dairy Queen" or "Take me to Costco", Siri almost uniformly executes that request correctly. Likewise, interestingly, it does pretty well with Yelp-answerable queries--if I say "How late is Sears open?", I get a correct answer for the local store. Basically, for the kind of directions or simple info I might need while driving, it does quite well, at least for me.
Asking about specific local businesses, particularly if they've got a very generic name or don't have a good Yelp listing, is a lot more hit-and-miss.
Yeah except I ask siri to take me to Home Depot and it directs me to a home depot that isn't even in my country! It takes me to one in Buffalo NY and I live in Canada, turns out it wants me to ask for THE Home Depot....