Competition is always good, and tablets with Google's Android OS could have a strong impact on the tablet market, said Jack Gold, principal analyst at J. Gold Associates.

"Android tablets within a year or year and a half could outsell the iPad. The market will be inundated with them," Gold said.

Some buyers are looking at Android tablets to get features such as cameras, Flash compatibility, USB ports and full 1080p high-definition video capabilities, which are some prominent features the iPad lacks.

The iPad started shipping in April and became an instant hit, and Apple reported selling more than 7 million iPads by the end of September. But companies such as Samsung and Toshiba are knocking on the door, and will soon release Android tablets that include features the iPad doesn't have.

Research In Motion and Hewlett-Packard have also joined the battle, announcing tablets running their OSes. will be out next year and run an OS it got through the acquisition of QNX. HP plans to release a tablet next year based on the WebOS mobile platform it acquired from Palm. Apple's iPad has also gained traction in businesses, and HP last week started shipping the Slate 500 business tablet, which runs on Microsoft's Windows 7 OS, and is priced at US$800.