Ethereal does work with Aironet 350 (and 340) series cards.
I've got it working fine under RedHat 7.3.
The most important thing is the drivers. If you use the latest Cisco drivers from cco, then promiscous mode does not work. You MUST use the drivers that ship in the Kernel build for 7.3 as these still have promiscous mode enabled.
Another piece of software called Kismet ships with two files called "cisco_monitor" and "cisco_unmonitor" that place the card in and out of promiscous mode.
This "modification" seems to be a change in a SRAM or some type of NVRAM register. Once the card is modified by Airmagnet, the firmware can be upgraded or downgraded and still works fine with Airmagnet. How can the internal SRAM or NVRAM of a Cisco 350 PC Card be accessed, read, and written to?