Thanks guys . Mission accomplished (sort of, look for a new post on lubricating the cable) I was pressing up on the small tab with the tip of a screwdriver all the while worrying I'd gouge the shroud, but the arm wasn't budging. I realized that while pushing on the tab, I was also pushing the arm at an angle to the shaft, which was preventing it from pulling straight off. I used a pair of water pump pliers to push up on the tab and allowed me to pull the wiper arm straight off.