Windows 7
I managed to get an offer for Windows 7 Professional for £30 (as a download only version - it is available to all people who are "students" or teachers or have access to an email address ending in .sch.uk or .ac.uk and a few others too) and since my Vista installation was both slow and the install of Vista Service Pack two was constantly failing, I thought it would be a good offer to waste the money. I did and this post is being written from Windows 7 Professional.
What is the difference between Windows 7 Home Premium and Windows 7 Professional? who cares - it has more features - most of which I will not use, but since they were both on offer for the same price, why would I go for the one with less features?