I've only seen 4 so far from this decade:
1. Elephant
2. The Pianist
3. Dancer in the Dark
Fahrenheit 9/11 is the only other one but I don't think it's that great nor deserving of the Palme D'or.
I am going to see L'Enfant and The Wind That Shakes the Barley for my upcoming Cannes Film Festival marathon this coming May during the festival. Hopefully as well as 4 Months, 3 Weeks, & 2 Days if it's out on DVD.