Ok, I found out the basics, but this may change in BackTrack 5. We'll be worried about support for Android devices then! I'll try to post a question.
For now -- here is the current state of existence with regards to WiFi adapter availability from inside a VM, regardless of BT4-in-Win7/Vista/XP or BT4-in-Linux/MacOSX.
Backtrack-Linux.org has an official page on Installing BT4 in VMware. However, this article doesn't specify VMware Player, VMware Workstation, VMware Fusion, VMware ESX, or VMware ESXi (let alone the version numbers). It should work in any of them, but here is a specific guide on VMware Workstation (probably 7.1 -- the latest). There's a nice little YouTube video in the comments section regarding VMware Player, which is nice -- but not extra informative in any particular direction (nor did any of the linked videos, as catchily named as possible, really relate back to the original issue, which is support of WiFi and aircrack-ng).
The main problem is that any WiFi card that works well with aircrack-ng (like the Alfa AWUS036H highly suggested card, which is external USB with the SMA antenna connector) must be USB in order to be accessible from a guest BT4 OS. There are a few comments in this link which discuss this absolute fact.
The good news is that in this article on Using BackTrack Linux 4 in VirtualBox, the most recent commenter says that:
When using VMware (or any hypervisor), you must use a USB wireless adapter.
If you are trying to use the host's built-in wireless device, you cannot use it in VMware (or any hypervisor) since the built-in wireless devices will be shown as virtual Ethernet adapters.
Read more: http://www.brighthub.com/computing/linux/articles/96323.aspx#ixzz1JZGPISeN
As an additional nicety, I am also listing two articles on installing the VBox Guest Additions in BT4 -- one from a blog, and the other from the BT forums.
While I don't see a reason to run VMware or Virtual-PC instead of VirtualBox (although I'll certainly try both), what does remain is that in order to complete certain attacks, such as MITM or frame injection along with monitoring maximum performance -- you will need 2 WiFi USB adapters, but it's been that way for Mac OS X and other platforms for about 4 years now.