Of course it will work if its GSM. If you read the article it said it is roaming on the Taiwan telco's network. Too bad after 2 months it will deactivate per the license agreement with ATT.
I'm planning on bringing my iPhone with me on my month long vacation in Tokyo, Taiwan, China, and Thailand in 2 weeks. All of them have AT&T roaming. I'm hoping to get by as much with Wifi only.
I'm looking forward to using Google Maps to get around. My biggest fear is getting jumped.