Vista is much prettier than previous versions of Windows. Its icons look better, windows have translucent borders, and items in the taskbar and in folders can display little previews of what they contain. Security is supposedly vastly better; there are some new free, included programs; and fast, universal search is now built in. There are hundreds of other, smaller, improvements and additions throughout the system, including parental controls and even a slicker version of Solitaire.
After months of testing Vista on multiple computers, new and old, I believe it is the best version of Windows that Microsoft has produced. However, while navigation has been improved, Vista isn't a breakthrough in ease of use. Overall, it works pretty much the same way as Windows XP. Windows hasn't been given nearly as radical an overhaul as Microsoft just applied to its other big product, Office.