IDC also points to economic slowdown as part of the reason for sluggish PC sales between April and June.

Gartner had a different take on the U.S. PC shipment slowdown, blaming mobile devices -- particularly tablets such as the iPad and Google's new Nexus 7. Consumers are less interested in buying PCs than smartphones and tablets, Gartner analyst Mikako Kitagawa says in a statement.

While tablets may not yet be able to replace all PC functions, the race between tablets and PCs will be an interesting one to watch over the next few years. Market research firm NPD Group predicts that tablets will , and the iPad long ago shed its initial reputation as a content consumption device. The iPad is already being used as a full-time workhorse by programmers and small business owners, and (along with a smattering of Android tablets) is becoming a common accompaniment of coffee shop patrons, subway riders, and air travelers.

Both Gartner and IDC also say that in any significant way. Ultrabooks are a new class of ultraportable laptops to energize the notebook market. The failure of Ultrabooks to catch on is due in part to higher prices. First priced at $1000 or more, Ultrabooks prices are only now starting to drop below a grand with the second generation of Ultrabooks powered by .