We are happy on XP/VISTA we have had no problems, we made sure that the hardware was powerful enough to carry VISTA (32 and 64bit) we dont buy budget systems and expect them to perform like power systems.
We ran and used WIN7 for three months sorry MS it was NOT liked in our enviorment.
Main reason all our computers/notebooks use the "CLASSIC" option available in XP and Vista, and MS decided to remove that option altogether.
So the choice has been made to stay VISTA, NEW hardware purchased recently has been "UPGRADED" to VISTA 64bit if we cannot purchase what we want from one supplier we will go elsewhere, and our existing/current supplier is only to happy to have our business, and give us what we request.