Apple has seen its new operating system received with rapturous approval after selling two million units in the first few days of availability, despite problems experienced by users upgrading to the software.

Many users complained about a Microsoft-like “blue screen of death”: a seized blank display that occurred during the installation process. The problem was blamed by Apple on third-party application “enhancement” programs.

Despite that issue, Leopard has won rave reviews, thanks in part to a host of new usability features. In a demonstration held last week in London, some of the most attractive appeared to be the stacked icons for finding files and programs; a jumping icon to show the location of downloaded items; and the Cover Flow and Quick Look file previewing capability.

Other key features include the Time Machine automated backup capability, and the Spaces tool for organising windows.

The additions along with the revival in Apple’s business outlook are encouraging some firms to look again at the vendor as mainstream business option.

“There are Fortune 100 companies looking again at Mac. Management people say [after using virtualisation that] it’s really cool, we’ll make it a standard option,” said Ben Rudolph of SWsoft, which develops the Parallels Mac/Windows desktop virtualisation program.

Peter Glock, head of solution development at Orange and a MacBook user, revealed that Orange and other firms are giving some users the option of a Mac and even when they have to pay a premium, adoption is high. Also, changes in computing patterns, virtualisation and the fact that Mac OS X is now fully 64bit and Unix, meant that Apple has more scope in businesses.