Apothecary is quite good. Just going pure apothecary gets you three provinces lightning-fast.
However, Apothecary chokes on green cards. If you have no green cards in your deck, Apothecary is somehwere between +3 and +5 cards, +1 action. Great card, gets your whole deck of coppers in your hand. If you have a few green cards, it starts choking - green cards accumulate at the top of your deck, and it soon becomes something like '+2 cards, +1 action, where one of those cards is a copper' or even just +1 card, +1 action, rearrange the top 4 cards of your deck, and the chain of apothecaries breaks.
Apothecary works well when there's a way to keep powering through that - when there's a way to draw the non-copper cards off the top of your deck easily. Here, crossroads and King's Court do that for you. You also used apothecary's rearrangement powers to a few times set up your next turn - like leaving a crossroads with a few green cards on the deck.
That said, Mountebank's curses could have made things a lot worse for you, but your opponent delayed getting a Mountebank; on the first shuffle he got a gold instead, and I think that cost him.
I'm no apothecary expert, but 6 provinces in 15 turns when Apothecary+good support is around is not surprising to me. (Not saying I'd be able to duplicate that, I'm pretty bad with apothecary, but such things can happen.)