as a software programmer i can tell you, there will never be a completly new sotware (in that case, windows). in the case of windows they always use the old kernels and improve them. also a software like an operation system is never completed. there are every time things to improve. things who have to be adjusted on the hardware or other software parts.
windows did some mistakes, but operating systems like me, xp or vista wasnt such bad. i worked long time with them and never hade problems. now i work on windows 7 64bit professionall and still have no problems. all ide's im using for developing my softwares are working fine, all my games are working fine, and all my movies are running smooth.
more my pc doesnt have to do. if i want a coffee, i go into my kitchen