It wasn't for me, at first I had no plans of getting the dock but then I had a short business trip come up that I didn't really want to take my laptop on but I thought if I had the keyboard I could at least do some work remotely and I found a good RDP app so I could connect to our terminal server.
But I do fully agree, if you can get the dock for free go for it. Its really nice to have, the battery life is awesome with the dock, still pretty good without too. Overall it just really depends on what you want to use the TF for, it just gives you options really.