The main complaint seen with Vista right from the start was the upgrade problems that people were running into on older systems especially premade only running 512mb to 1gb of memory. After the 6yr. gap between the two versions MS had wrapped Vista mainly around the newer capabilities seen with the latest hardwares at the time of it's release.
In order words MS later came to the realization that the OS was becoming too large and worked on developing the new WinMin kernelr to refine the Vista kernel down as well as "trimming the fat" as far all of the background services running in Vista. Despite the obvious best recommend for 2gb of ram on Vista you saw far fewer errors in gaming and other programs in the 2yrs.+ since it was released when compared to constant problems that were typically seen in XP in less then half that amount of time.
With 7 there's no excessive promotion for the new version with the articles there. Since the beta releases were first run here along side both XP and Vista it didn't take too long to figure out which would prove itself to be the actual best of the three when being run together side by side. The conclusion was reached by the RC stage which was going to be the predominant OS with XP then removed! Vista is still an option for a secondary OS.
As for the new direction MS decided to take with 7 I think this old 2007 article at InformationWeek sums things up quite well.
"Microsoft Wants Smaller Software Footprints Starting With Windows 7"
Microsoft will use a bare-bones version of the Windows kernel, called MinWin, as the starting point for the development of future products, including Windows 7 and Windows Server. By Paul McDougall
InformationWeek October 19, 2007 10:52 AM
"Microsoft (NSDQ: MSFT
) apparently is putting its Windows operating system on a diet.
Acknowledging criticisms that the Windows operating system is "bloated," a senior company official said the software maker has adopted a new, modular approach to OS development that will yield more streamlined products beginning with Windows 7 -- a successor to Windows Vista that's expected to be available some time in 2010.
"We're starting on this path," said Microsoft distinguished engineer Eric Traut, during a presentation at a college campus.
"A lot of people think of Windows as this large, bloated operating system. That's maybe a fair characterization," said Traut, who was speaking last week at the University of Illinois. A video of his presentation appeared Friday on the blog IstartedSomething.com
With an eye toward offering slimmer products, Microsoft will use a bare-bones version of the Windows kernel, called MinWin, as the starting point for the development of future products, including Windows 7 and Windows Server.
Microsoft programmers will use MinWin as a base for development and then layer on only what's needed for particular Windows versions. "There's a really nice little core inside Windows," said Traut.
In adopting a more modular approach to Windows development, Microsoft may be bowing to criticism that current, one-size-fits-all versions of the OS are overstuffed for many user requirements. To prove his point, Traut demonstrated a version of MinWin built on 25 Mbytes of data, compared to Windows Vista's 4-Gbyte footprint. "We've taken a shot at stripping out all the layers above and making sure we have a clean architectural layer," said Traut.
Microsoft has no plans to "productize" MinWin, but will use it as the basis for future OS development. "We're definitely going to be using this in a lot of the products we build," said Traut.
Microsoft may be hoping that the Windows-on-Weight Watchers approach will help it fend off competition from Linux and Web-based software -- non-Microsoft computing alternatives that impose less demanding hardware requirements on end users. Despite the fact that Windows Vista launched earlier this year amid considerable hype, many consumers and businesses have shied away
from the OS, citing cost and compatibility concerns, in addition to Vista's steep resource requirements." Microsoft Wants Smaller Software Footprints Starting With Windows 7 -- Microsoft -- InformationWeek