Any wireless NIC that supports 108 Mbps uses the Atheros SuperG chipset, which is fully supported in FreeBSD since 6.0 was released many many moons ago. This is the best supported chipset in FreeBSD. It's only 802.11g. But, if you have a wireless router that supports 108 Mbps (aka a SuperG router), then you will get the full 108 Mbps throughput. Otherwise, you'll be limited to the standard 54 Mbps of 802.11g.