To save you some trouble of reading the old threads....
Double clutching is slower then normal shifting, don´t do it, it´s dumb (unless you have a synchro-less racing tranny, and even then...). If the car you plan on driving is from the mid 40´s, then sure, double clutch all you want.
"Driving is like a narcotic, an addiction that can take over lives. It ruins people, breaks families apart, and even kills. It’s habit that needs to be fueled. Time, money, rationality, sweat, knuckle skin, and anyone who disapproves are of little importance to a driver, and are often overlooked. Hi, I’m Nelson, and I’m a drivaholic."