Yes, wifi is supported, since day 1. Normally, you should be able to see
a NetworkManager icon of the netvm (so in a red rectangle) in your tray,
as illustrated on this screenshot:
http://qubes-os.org/Screenshots_files/snapshot6.png
If you don't see the NM's icon, then:
1) Check if your netvm is running (use qvm-ls or the qubes-manager)
2) Run the terminal in the netvm (qvm-run netvm gnome-terminal, or right
click on the netvm in the manager, and choose "Run command in the VM...)
3) Check if you can see your Wifi device in the netvm (lspci)
4) ... and check if you have the wifi interface (ifconfig), and whether
there are any wifi-related errors in dmesg. The latter might be caused
by Xen not getting enough continues memory for the netvm SWIOTLB buffer,
in which case the wifi driver wont load. In this case, try restarting
your system, or add more RAM :)
joanna.