I'm running Vim / IntelliJ Idea all day long for last few years and wouldn't ever get rid of one or the other. You can use a plugin to have some Vim-like capabilities in idea, but then - when it comes to working with text files (not project files) / ssh / work on remote servers, Vim is my tool to go.
If Notepad or Visual Studio works the same way for you, then you should be happy that you found a tool that works - price has nothing to do with the quality of the tool and quality of the tool has nothing to do with how productive you are when you're using it.
Their community edition (which, by the way, is awesome, even without the features from the Ultimate edition) is released under the Apache 2.0 license, and many of the features they develop end up in the community edition. The source code is here: http://www.jetbrains.org/display/IJOS/Download
For example, Google's Android Studio is built on top of IntelliJ IDEA community edition.