The Asus Eee Pad Transformer, the company’s 10.1-inch Honeycomb tablet that hooks into a keyboard dock, went on sale in the U.S. Tuesday with a $399.99 price tag.

And just as quickly, it sold out.

. The tablet is listed as being out of stock or unavailable at online sites such as Amazon and NewEgg and at the Web sites of several major retailers including Best Buy, Target and Walmart.

The 16GB WiFi tablet entirely sold out in Britain, and Asus had to issue a statement promising more shipments in late April or early May.

Early reviews of the Transformer in Britain and the U.S. have been good.

CNET’s Eric Franklin gave it 3.5 out of five stars, putting it on par with other Android tablets the site has reviewed such as the G-Slate, the Xoom and the BlackBerry PlayBook. Franklin’s main criticisms were that the tablet was not very comfortable to hold, and does not have good video recording or playback.

On the other hand, it is the cheapest Honeycomb tablet on the market and its ability to transform into a netbook via a $150 docking station may add to its appeal. Adding the docking station gives you an SD card slot and two full-size USB ports.

Engadget’s Vlad Savov had high praise for the tablet’s software and its e-mail, weather and date widgets, when it reviewed the British version last week.