I ordered one of these with my ENVI 128, confused that it might have turned up late after I received my main unit I found it enclosed in the box with the ENVI.
It worked out-the-box on Ubuntu Karmic, detected as a USB serial controller and attached to ttyUSB0 (iirc), running 'cat /dev/ttyUSB0' immediately read off the XML stream in all it's glory.
No problems with the build quality unlike the ENVI itself, a more general-purpose USB serial controller with a DE-9 connector would have been nice but you can't have everything.