Windows 7 looks all fine and dandy right now. It looks good - brilliant, even. Its design is probably the first in Microsoft Windows history to actually be able to rival that of the great Mac OS X... but it's still going to suck. Let me tell you why:
All versions of Redmond's Windows operating system have been plagued by a technology that underpins the operating of the system - the Windows Registry. This piece of software manages the existance and execution of applications on the system - by storing special "Registry Keys" that contain information pertaining to application settings, as well as special keys designated to the installation of files on the system. It's basically the backbone of Windows, and it's also very much prone to getting corrupted very quickly.
It is, nine out of ten times, the cause of messing up your Windows experience and resulting in a re-install of the system. It gets corrupted mainly because when you install and uninstall software, the registry manages all the application's keys in a very complex manner. So uninstalling software can result in the system not removing certain keys (usually because it deems them necessary for other applications). This corrupts the integral part of the Windows system.
Now this type of technology is kind of "obsolete" in today's modern world. Modern operating systems like Mac OS X and Linux (because Windows is not, contrary to popular belief, modern - its core, NT, is over twenty years old!) have more intuitive ways of managing applications on the system. Microsoft has yet to jump on the bandwagon and develop a more stable way of managing their applications, and thus making the OS more reliable.
So that's why Windows 7, with its corrupt-prone Registry, will still suck in the long-run.