More powerful netbook models will likely make their way to market in 2009 and 2010. And that's another reason for businesses to wait, said Gartner's Fiering.

"There is no system or platform stability," Fiering says. "The models are going to churn very quickly, so it's a little bit early to think about buying them for your workers."

The current top dog of the netbook pack is Acer's Aspire One, according to data from DisplaySearch. The top model on Amazon.com's laptop list has a 1.6GHz Atom processor, 8.9-inch screen, 1GB of main memory, a 160GB hard drive and comes with Windows XP Home. The netbook, which weighs 2.2 pounds, sells for under $400.

Asus, which fell behind Acer in sales of its netbooks, sells a similarly configured netbook, the 904HA, for under $400. It also makes a larger version, the 1000HA, with a 10-inch screen. Both weigh slightly more than 3 pounds.

HP and Dell have also entered the market. HP's sub-$400 notebook, its Mini 1010NR, has a 8.9-inch screen, 512KB of main memory, a 8GB solid-state drive, comes with Windows XP Home, and weighs 2.4 pounds. Dell has a nearly identical sub-$400 configuration, the Inspiron Mini 9, weighing 2.3 pounds.

One certainty: The evolution toward smaller devices will continue, says Fiering.

"It has been going on for the entire history of notebook computer," she says. "I remember when the first sub-10-pound notebook came out, and I rushed out to buy it. The Holy Grail is to have something the size of a Blackberry that has all the functionality that you need."