After all the fun and playing around with flappy paddles for a week, you're still going to end up sticking it in D and driving it like an auto. I personally think the manual mode is just a gimmick. You'll never get a proper manual mode with an auto box. Plus you can't engine brake, slip the clutch etc. These are the main reasons why I sold my DSG R32 and got a manual GTI. And they're expensive to fix!
....Anyone who
only drives their DSG in D-mode all the time isn't what I call a 'driver' and it's very doubtful they are an enthusiast or even enjoy driving. It's stupid not to use all the options which are available to enjoy and suit all kinds of driving circumstances.
It's as sub39h says, you
can engine brake. Slipping a clutch will cause excessive wear and damage. Do you like traffic light grand prix? On approved dragstrips you can use DSG's Launch Control if it helps you.
Again, I'm not saying that one system is better than the other - It's personal preference. But DSG and similar systems are far from being a gimmick.
As for expensive to fix, 100k miles on mine with no DSG costs so far - How many clutches would you go through in 100k miles of slipping it regularly? A car is built out of thousands of parts - Anything can fail and they all cost money.