Things are very different with Windows Vista. Microsoft deserves praise for the work it has done on Vista’s installation program. It works much better than any of its predecessors, and for several reasons. That change brings about a whole different set of good news and gotchas when considering your Windows Vista upgrade strategy.
This article discusses a lot of the facts that people already know, but the author highly stresses checking with the Upgrade Adviser from Microsoft before upgrading, to make sure you won’t be regretting it later.
Source: Computer World