I used the skills I learned at SCREEN for the first 8 years or so of my career when I worked as a software engineer. Now that I work in Professional Services, I rely much more on the interpersonal and cultural skills that I learned in Japan and a little bit on the language skills. I have had wonderful work experiences in Australia, Ireland, the UK, and Sweden, and these experiences would have been much more challenging had I not spent time in Japan. I definitely used my cultural skills in each of these countries--not that the cultural gap was as large as in Japan--and I most certainly used my language skills in Sweden, where learning to read was a high priority, especially for groceries.
Even though I have not been to China, I can most certainly tell you that learning Mandarin was much simpler since I was already semi-literate in Japanese. I was the only student in class who could say, "Everything is pronounced exactly like it's spelled." :-)
I do look forward to one day working either in Japan or with the Japanese again. It was most certainly a positive experience the first time.