Even if Sun Fire x4100 and x4200 servers will be officially supported for local booting just since the upcoming ESX Server 3.0, VMware already released a special driver for LSI 1064 controller which works with the new ESX Server 2.5.3.
Download the driver here and read the related Knowledge Base article here.
The availability of this driver time ahead official release means a lot of customers demostrated insterest for the new Sun servers, never supported by ESX before.
I believe Sun hardware will gain a lot of popularity at ESX Server 3.0 launch time.