I like to take my time shopping. Look around read labels, check what are people are buying.
The part that kills me is checking out. I have always wondered why the cart can't scan your items and when you push it through a reader at checkout it just has everything totaled and charges you. The cashier can now bag your groceries. You could even have the cart recheck your purchase amount when the items are removed to be packed.
Someone out there hurry up and figure out the details :)