i have the same problem and want to use UDP for OSC communication.
so i bought a mega 2560 and the Arduino Wifi Shield cause the description says
An Atmega 32UC3 provides a network (IP) stack capable of both TCP and UDP.
Use the WiFI library to write sketches which connect to the internet using the shield.
i searched al lot and tried to rewrite the EthernetUDP Class. no success
but my skills are not good enough.
would be really great if someone can help ?!?
here i found out that the last update is about 4 month ago...
perhaps the admin can show some beta code in the branch.https://github.com/arduino/wifishield/tree/master/libraries/WiFi