Buy the expansion. You get more words to keep the game fresh. It allows you to have a set of clues on each side of the table along with another timer. This speeds up the game and it helps it out a lot. I love this game.
Very good idea to get a second timer as we sometimes find a word quickly and had to wait for the timer to expire, causing a lull in play. Getting the second timer surprised me at first as I thought it was a waste, turns out it's the best idea they could've had. Needless to say that you don't need the expansion to get a 30sec. timer, but the categories are original and totally worth it!