This thread inspired me to look into this and read my manual as I had been thinking about it for a while before. Wet/Sport, winter/summer etc. I have to say I actually notice a huge difference between the two and thought that it actually also made a difference to the sequencing of the gears as well as changes to the ESP or something as it seems far more responsive in Stadard and more ground hugging in Wet.

Looking at the manual it does state do not change switch whilst driving as this could cause a change in handling that you were not expected.(not exact words but something of the like)

SOO does it change just the gear ratio and the starting gear? or is there also a change to the handling systems too?

Sorry in advance if this reply is not using the correct technical terms LOL