Yes, I double declutch because my car benifits from it. Otherwise it jerks a bit on the down changes. I've got a pair of Puma Futurecats which make fantastic driving shoes. ;)
And I drive in my skater shoes, or my greezy nasty work shoes that slip off the pedal before it touches the pedal (great for driving a clutch *sarcasm*)
Getting Bolt-on pedals can help too. I got some for my car. Don't hate me cuz I drive auto - I hate dealing with traffic! I don't need to heel/toe but here's an example. The brake pedal's shifted over to the left about an inch - i didn't like the feel of my shoe barely fitting inbetween the brake pedal and the sidewall - that's how much larger these are.
Also, I would rather drive barefoot than in flip flops.
I use it in some situations, but when I do most people give me wierd look, and I almost got pulled over for hitting the gas a little to hard when I down shifted.
i use heel-toe a lot, but lemme tell you, in an old Mini with no gas pedal mod, its interesting... size 14 shoes plus that tiny pedal means you cant miss the pedal, but its still kinda wierd Its simpler than in teh Supra, but more effective and more fun