If we play a board that has Workshop and Garden kingdom cards, I almost exclusively play them as my strategy. In the early game, I focus on buying Workshop and by the third round I typically get two "buys", one in the Action phase with Workshop and the other in the Buy phase.
Mid-game, I switch to buying Garden (which gives you one VP for every 10 cards in your deck) and if I have less than 3 coins in the Buy phase, I get an Estate or Copper. This strategy has proved to be almost 100% effective in rushing to deplete three decks and ending the game around turn 16 or 17. I've only lost once or twice using this strategy and it's usually when I deviate from my plan and forget to pick up an Estate/Copper or pick up another card on a whim.
For this scenario, I'm only playing the base set and the third pile I'm depleting is Estates.
What are effective counter-strategies to a Workshop/Garden strategy?