It works well. (Score 4, Informative)

Its all in the connectivity and the speed of the device getting the call packetized and placed on the wire. I use my softphone on my laptop with a 802.11b PCMCIA card at home through a Juniper SSL VPN with consistant success and quality. I have installed VoIP phones that connected to a gateway for call setup and tear down over a wireless bridge with good success. I have also experienced the mediocre quality of the DialPad's/Net2Phones etc.. If the device doing the codec compression can get the packet on the wire fast enough and there is enough throughput for the call. The call will succeed and be quality, WLAN's included. If the network is already taxed and the device doing the codec compression/and or call setup and teardown is taxed (in the case of some of the VoIP providers) the call will suffer.

VoIP over WLAN has just started. If you work for an intrenched Wireless Phone provider or a Baby Bell you wish that VoIP over WLAN was dead and this is probably just the beginning of the FUD from these guys and their pawns in an effort to hold on to their customers. So my answer is no.. its not dead.