In the majority of cases, waiting for confirmations is a waste of time. The difficulty in pulling off a double-spend is so convoluted and tricky, I don't think waiting for confirmations is worth it unless you're dealing with huge inter-bank or inter-business transfers. I've made purchases with Bitcoin about a dozen times now, and each time only took a few seconds. I think the longest transaction was about 7 seconds. Most were practically instantaneous.