Hardware manufacturers seem to be obsessed with rejiggering the internals of their products without putting any markings on the packaging (or hell, on the card, or even in its top-level PCI information) to indicate that something has changed. This screws Linux users on a regular basis.
The particular case in point–which I suggest you avoid–is the Netgear WG511. The original (v1) iteration of this Cardbus 802.11g card used the Intersil PrismGT/Duette chipset which is well-supported under Linux–it has a driver (prism54) that’s been in the kernel for several months now and it’s apparently fast and reliable.
Unfortunately, some time recently, Netgear (and apparently other manufacturers, including SMC) started using the Intersil Frisbee in these cards. This chipset, though it declares the same PCI ID (but a different “subsystem ID”), is not compatible with the GT/Duette chipset.
So, to review: the external packaging has no distinguishing markings, the card itself has no distinguishing markings, and the PCI information only indicates that it’s a different “subsystem”.
Avoid this card at all costs!