I'm loving the little Carista at the moment. I was like a kid at Christmas, so was flicking 'switches' left right and centre:
1. Needle sweep at startup/ignition
2. Unlock *all* doors (not just the driver door), with just one press of unlock on the key.
3. Allow configuring of daytime running lights via dash display (MMI)
4. Lower passenger-side mirror when in reverse gear
5. Blink turn signals when done closing windows via remote
6. Use tail lights as daytime running lights (Norwegian mode)
7. Enable hidden menu (hasn't yet worked - talking to Carista about this one)
Should all the be 'safe' and there are a good number of VAGCOM settings it cannot yet access that could be considered unsafe.
In fact, I did see one setting that popped up a warning about it potential conflict with european safety or law, so it shouldn't be possible to make an unsafe modification without you having to specifically agree to it first.
I'm not sure about the dealers - One thing I am given to understand is that any dealer update to the car's systems may reset some or all of these settings to factory, so it's worth noting the changes you make and checking them after it's been in for a service etc.
I have a tiny bit more raw power than the A3 2.0 TDI I came from, but because the car is bigger and heavier, I tend to drive it in a more sedate manner, as I've discovered some tricky torque steer and understeer issues if I try to push it too hard.