I managed to flash a WP34s, after having all components (the cable and the calculator of course). It went without problems from the first time. Well, the only problem was finding a Windows machine, since in Wine the port COM1 refused to show up in the Samba v2.9 program, even when linking to /dev/ttyS0 in ~/.wine/dosdevices.
I'll just be honest, the custom key labels I stuck onto it are a pain on the eyes due to being too small and low contrast, but they're easy to remove.
One day I hope to be able to write a multiplatform program that can flash ROMs to this calculator through the serial port, and, to write different ROMs to put on this nice piece of hardware :)