The OQO is not the only handtop computer (small computers that run full versions of Microsoft Windows XP) out there today. Here is a list of alternatives.
Here is the FlipStart:
The Sony U50 (in Japanese):
Although this is reportedly dropped to make way for the Sony U750.
Here is the Antelope:
And this is the Tiqit:
Finally here's a product comparison from Handtops.com.