I disagree, I don't believe it makes things any quicker, in fact it slows things down.
The local supermarkets have got entirely self service checkouts, which are almost always slower than going to the cashier for two reasons.
1. Supermarkets don't trust you, all your food gets weighed after scanning which takes much longer than it should.
2. Cashiers have been trained to do their job, and have had hours doing it, so they should be able to do it quicker than you can