I initially attempted to make my own project work with a Liksprite CuHead, which is a Clone of the Asynclabs WiShield. I got it to work to some degree nut could not progress beyond a certain point, e.g using certain libraries with the CuHead.
Then I tried a Diysandbox.com Hydrogen. Nice and capable product, but in the end I came across the same problem. If you do go the WiFi shield route I'd recommend this one. I have no experience with the Arduino Wifi Shield, which I believe is certainly a very capable piece of hardware nut it will take some time until libraries for it are fully developed and debugged so the maturity of approaches that of the Ethernet Shield.
I finally decided to try using a little WiFi router ( TP-Link WR703n) connected to the Ethernet card and I can assure you that this is dead simple!
The reason is that the WiFi connection is transparent for the Arduino, so you can take advantage of the Full functionality of the Ethernet library and many other libraries that depend on the Ethernet library like DHCP/Bonjour or ArdOSC.
Further more , if someone else less technically inclined wants to reconfigure the network then they can simply reconfigure the little router through its Web interface. No need to hack around in Arduino code, no compilation and upload.