Twenty-one months have passed since Windows Vista was released. So, how much and what do we know about it? Obviously, home users hate Vista, businesses uninstall it and move back to Windows XP. According to Gartner Inc. it is proof that the 23-year-old Windows line is falling under its own weight. Microsoft feels the negative user feedback from Windows Vista and is working on the engineering blueprint for Windows 7.
At the same time, predecessor Windows XP, which Microsoft stopped shipping to retailers and the major PC makers on June 30, has over time become so favoured that it's gathering more calls for "unretirement" than NFL icon Brett Favre has done in his wildest dreams this summer. But all of the griping about Vista and the immediate nostalgia for XP conceals the uninteresting and statistical reality: XP itself has been slow in becoming popular with users. Perhaps even slower than Vista was thus far.
Nevertheless, even Gartner is predicting the fate of Windows. He forecasts that Vista is going to be more popular at the end of this year than XP had been at a similar junction with 28% of the PC operating 
system installed base worldwide, versus 22% for XP at the end of 2003.
Then there were all the security issues. At present, XP is supposed to be highly secure, though that was not the case in 2002. That's when Life Time Products Inc. upgraded to the operating system after Microsoft released Service Pack 1, its first bug-fix update. In order to try to resolve the security problems, Microsoft developed a second service pack, which it forced customers to adopt. But, there were two problems.
First, not everyone was convinced that SP2 would be a security cure-all, a view that was partially asserted by later growth. Another Forrester report, by a different analyst, cites a "new trend" of upgrades from XP to Vista. It also advises that getting rid of Vista in order to wait for Windows 7 would be a mistake. Second, SP2 has been such a major modification that it broke applications, many of them, particularly enterprise ones.
As part of the Windows 7 development process, Sinofsky from Microsoft said that Microsoft is paying special attention to performance parameters like memory usage, CPU utilization, disk I/O, boot, shutdown, standby/resume, and the operating system footprint. Many of these functions caused problems for Vista users, particularly those who migrated before Microsoft's release of Vista service pack 1, in February. Sinofsky offered that Microsoft is well informed of the wide-ranging requirements of Windows users and is going to pay respect to the Windows 7 development process.
Resources:
Is it possible for Vista to have its days like XP finally did?
Is Microsoft going to fix the problems in development of Windows 7?