I bought this so I could be fully charged and connected while travelling.
The adapter lets you convert basically any power plug to any other. I have used it in the US and Europe to convert my UK power plug to the local power converter. While in the US you can pop off the cap and use the twin USB charger at the same time. So overnight I could charge my laptop, and also charge an HTC Desire and iPhone (using the appropriate USB cables) using the USB adapter.
If I could change one thing, it would be the dual USB charger adapter cap. You can only use this independently while in the US as it will only plug directly into that type of two prong socket. If you want to use the USB charger in the UK you need to plug it into the body of the main adapter. I suppose this is to save space due to the bulky UK plug.
Anyway, it's the only adapter I travel with now. Recommended!