The 401 is based on the Intersil Prism II chip set and the clearly written Reference manual says that it's both 16-bit PCMCIA and 32-bit CardBus compatible and works in any available PCMCIA or CardBus slot. The antenna is non-detachable, unmovable, and flat enough to not interfere with the adjacent PC card slot, either above or below it. There's one "Link" LED on the antenna section, which shines steadily when the card has a wireless network "Infrastructure" connection and blinks when it loses signal, or is operating in "AdHoc" mode (see this page if you need help with these terms.) The LED doesn't flicker to indicate network activity.
Drivers for Win95/98/NT/ME and 2000 come on a CD, along with PDF and Word versions of the reference manual. There's no mention of support for other OSes in the Reference or Installation Guide, but a Linux WLAN and PCMCIA driver "tar" files and a short ReadMe file are on the CD. If you go the way of the penguin, you're probably on your own.
Tip: Reader Mayly Sanchez didn't have much luck with the Linux driver that NETGEAR provided, but said this one worked fine for him.
Installation on my Win98 Compaq 1650 laptop went relatively smoothly and I found that the drivers installed in such a way as to connect to the NETGEAR ME102 Access Point (reviewed here) without having to touch any settings. If you do need to adjust settings, the Reference Manual has good explanations for each of the settings that you can futz with.
Although the card connected fine to the ME102 access point, I noticed that the ESSID field was blank. This probably should have had an entry of "Wireless", which is the ME102's default ESSID.
Tip: See this page if you need help configuring the card to work with an Access Point, or this page if you are trying to get a card-to-card network working.
The Configuration Utility supplied with the 401 is the ubiquitous Neesus Datacom Wireless LAN Configuration Utility. I've complained about this program many times before, so go here if you're unfamiliar with what it does (or doesn't do).
The only other things you need to know are that the 401 supports both 40 and 128 bit WEP encryption and that the driver supports roaming among Access Points.