||InDesign's graphics engine was built from scratch upon Apple's new Quartz drawing engine; Quark was left supporting an engine based on the Classic Mac OS' QuickDraw drawing engine. In order to catch up with features like alpha layer transparency, Unicode support, and advanced typography, Quark had to gut XPress and rewrite it, but they didn't even get started until InDesign's new engine was already fairly mature, leaving Quark with a handful of technology IOUs, while Adobe sold their users on InDesign's superior compositing performance.
Coincidentally, the most significant change in Windows Vista revolves around Microsoft's new graphics compositing and display engines: the Windows Graphics Foundation and the Windows Presentation Foundation, roughly equivalent to Apple's Quartz 2D drawing engine and the Quartz compositor.
Apple completed their graphics engine as part of the initial development of Mac OS X five years ago, giving Mac OS X's Quartz compositing and display technologies a half decade lead. Microsoft's efforts are hampered by requisite backwards compatibility with GDI/GDI+, while Apple could largely start from scratch in engineering Quartz.
Apple hasn't sat on their initial lead either, but instead moved on to deliver accelerated Quartz Extreme using OpenGL to move compositing to the specialized graphics processor, and most recently, moved additional 2D drawing and video processing there as well with Core Image and Core Video.
Microsoft has expressed less interest in the OpenGL standard and instead focused on their proprietary DirectX and Direct3D. They are building OpenGL support in Vista on top of Direct3D, which will is expected to result in OpenGL performance as much as 50% worse than Windows XP.
All of which leaves Microsoft in a difficult position. Nothing they can release will woo the industry in comparison to Apple's lithe Mac OS X. The best they can hope for is a favorable comparison, but the problem with being compared at all means that Microsoft, for the first time, has real competition, and even worse, competition that is setting high standards. Microsoft is no longer competing just against time.
Further, Apple's foray into Intel based Mac hardware means that Microsoft's established monopoly as the operating system installed on all new PCs sold is in danger as well. Suddenly, even customers beholden to buying x86 hardware will have the option to buy hardware from Apple, and alternatively use it with Microsoft's Windows or Mac OS X.
That significantly lowers the barrier of entry for Mac OS X on the desktop; customers don't have to fully invest in Mac OS X. They can safely try it out on hardware that is also compatible with their existing Windows software, or roll out Apple hardware to both Windows and Mac OS X users, and directly evaluate the performance of each. Windows has never before had to directly compete against the Mac OS running natively.
For users, this means Microsoft, like Quark, will have to scramble to stay competitive. It also means Apple will have to work hard to maintain a competitive edge, as well as deliver compelling hardware in order to take advantage of their biggest break ever. Microsoft's not poised to crumble into oblivion just yet, but competition will certainly make things interesting again.