Packet One is launching WiMAX on August 19 2008.
As mentioned here, the coverage areas are KLCC, Golden Triangle, Pekelliling, Setapak, Gombak, Seri Rampai, Sentul, Pudu, and some areas in Subang Jaya,
Possibly 4 packages will be offered-200Kbps, 500Kbps, 1.2Mbps and 2.4Mbps
All of these packages comes with a desktop modem as picture below(or video here) and do expect a 2 years contract.
Official report of the launch will be on the Mobile World website.