I just wanted to add a Me Too! to this.
I bought the Symbol card from ShirtPocket (mine actually says it's a Symbol Spectrum24 HighRate Wireless Networker, P/N LA-4137-1020-WW if that helps any). It did NOT work with the "stock" (ShirtPocket-modified) Japanese ROM, but works fine on the Cacko/QT 1.21 (a & ROMs, almost out of the box.
..I say "almost" out of the box, because I personally had to do some dabbling around to get WEP working properly, and adjusting config files to get Opera to pick up http proxies etc.
I was impressed that ShirtPocket took the trouble to phone me and warn me that the card might cause problems in the stock ROM, and offer to swap for a known good card. Since I'd done my research, and was prepared to dabble I declined the offer and, with the terribly minor caveats above, I've not had cause to regret that decision at all...