I am curious to see if there are other VI users out there... and if so, what IDE/plugin do you use? I'm getting tired of this Eclipse plugin... just wondering if IntelliJ, Komodo, XCode, has (better) support of it. :)
In my opinion, code completion, refactoring support, integrated source control and debugging are compelling reasons to learn an IDE. Modern IDEs (Eclipse, IDEA, VisualStudio, etc.) significantly accelerate development and make code safer by providing integrated test support, code hints, etc.
As much as I like vi, I hate to admit this 808blogger, but I'd choose a IDE without vi support because of all the aforementioned that Daniel says. Though, with Rails development, one of my coworkers swears by Pope's plugin (http://rails.vim.tpope.net/) - I still +1 for IDE. :P
I tend to use the editor that is on the machine I am using to do the coding. I really like naked vi and have been using it for 20 years. When I did my Master's I used vi and nroff as my word processor. I also use Eclipse and Visual Studio when they are applicable to the task.
Intellij is the only IDE that I know of that has decent VI key support... via the IDEA VIM plugin. It's free and it works. Moreover the key binding capability is powerful enough that you can easily customize things to your liking (e.g. you don't automatically lose all of the editor shortcuts when you're in vi mode).