I had a go with IntelliSync (the SL version) connecting to Opie on my Zaurus this evening. I found that despite being a little hard to find, IntelliSync is in fact still available for download, which is good because the CDs that came with my Zaurus are in Japanese only. Thankfully the installer does not require any licence keys or device presence in order to install.
The next thing was to get the USB network connection working in Windows. I plugged in my Zaurus, Windows popped up the usual dialogs and I fed it the usual linux.inf file which it accepted. Unfortunately though after a delay the result was the error "This device cannot start. (Code 10)". There are numerous references to this error message on the web, but I couldn't find a satisfactory solution amongst any of them. (Of course USB networking between my Z and my laptop when running Linux works perfectly.)
I decided to simply press on and try to get IntelliSync to connect to my Z over WiFi. Despite only having USB and Serial options for the connection type and it insisting on not allowing the IP address of my Z (192.168.0.5) I was finally able to coerce it into connecting by specifying an address of the same length that it would allow (eg. 192.168.1.1), and then editing the file NetStat.dat with a hex editor to change the address. If you then go to the connection settings and click OK the change should be permanent.
This is not enough to actually get it synchronising however - it's obviously connecting, however all you get is a quick flash of the sync screen on the Opie side and then an error with the suggestion to "check the application version" from IntelliSync. Presumably this means that Opie is not sending the responses that IntelliSync expects. I suppose I will have to analyse the traffic in order to fix this.