Gamasutra reports that, at least in the EU, the Nintendo DS has the portable war pretty much locked up
for the time being. 200,000 units of the DS Lite were sold in the ten days after its launch. From the article: "According to Nintendo of Europe, the Nintendo DS has now secured the lead in the handheld market in Europe, with sales of the format exceeding 5 million. No sales figures from Sony are available to compare directly, with only a "shipped" figure of almost 6 million for all territories bar North America and Japan."
Interestingly, 136,500 units were sold in the United States in just the first two days after the handheld console's launch.