Vista was aimed to be installed on home pcs and used by people with little or no previous computer experience. There is no argument that it wouldn't be the OS of choice for a professional developer. But, sometimes it's not a question of wanting or not wanting to install it. In many companies, you're not given a choice and have to use what they give you, or what they have licenses for. Sometimes, you have it so you can develop a product specifically for it - most of the newer games are written and optimized for DirectX 10, which only exists on Vista, and sometimes people install it just to check it out or have dual boot.
I'm not going to advocate picking Vista over XP or the other way around. The simple truth is that the vast majority of new computers are sold with Vista pre-installed, and most non-experts will not bother with re-installing the OS, so Vista will remain the de-facto "most popular" OS and we all just have to deal with it.
Bookmarks