updated 10:24 pm EDT, Thu October 24, 2013
Users can leap directly to Mavericks, or take it in easy stages
As it did with Snow Leopard, Apple has begun offering voucher codes for downloadable versions of Lion and Mountain Lion for sale for those customers who don't wish to "leap" directly from Snow Leopard to Mavericks, offering an easier path for users who sat out the last two major releases due to incompatible software, files that needed to be converted to modern standards or other reasons. Recently, Snow Leopard was still seen to account for about 20-25 percent of the entire Mac userbase.
Snow Leopard is currently still available for the remaining few that have eligible machines but have not upgraded. Some, of course, are still working with PowerPC-based machines that can't update beyond Leopard (10.5.8 was the final release for that OS), but together that group accounts for perhaps as much as four percent of the active Mac userbase.
For security reasons, Intel Macs that are not already running something later than Snow Leopard are recommended to upgrade to it at a minimum, as it continues to receive important security and compatibility updates. Traditionally, Apple has rarely offered support for more than two previous operating systems plus the current one at any one time, so it will be interesting to see if the company slowly drops support for Snow Leopard in favor of Lion and Mountain Lion.
The two downloadable-only previous OS releases are priced at $20 apiece. Lion introduced a number of significant changes that are now standard features in OS X, including on-demand scrollbars, "natural" scrolling, multi-touch gestures, autosave and versions, fullscreen apps, AirDrop, Launchpad, MIssion Control and other features. Apple's original implementation of autosave and versions in Lion -- eliminating the "Save As" button in Apple apps like Pages -- wasn't especially popular, but was returned (albeit hidden) in Mountain Lion.
Mountain Lion was, as the name implies, to Lion what Snow Leopard was to Leopard -- a refining of the same basic OS, but with significant under-the-hood changes to prepare for the future. Major features included integration with iCloud, streamlined sharing to social services and other destinations, transitioning Software Update to the Mac App Store, and refinement of any of the concepts and features introduced in Lion.
The availability of Lion and Mountain Lion will also make it easier for users who are looking at significant software upgrade costs in order to bring their aging applications or data formats into conformity with current standards, or who feel that their older machines -- while compatible with Mavericks -- would be better served with an older system running contemporaneous software and will upgrade to Mavericks when they upgrade to a new machine.
The voucher codes can be obtained only through Apple's Online store. The code can then be redeemed on the Mac App Store for the actual file, which is not visible to users who don't have the voucher code. Having access to the Mac App Store -- which requires OS X 10.6.8 -- is still required. Users who need to upgrade to Snow Leopard should contact Apple by phone to order the Snow Leopard DVD, which also sells for $20.