My use of an IDE usually depends on two factors, the complexity of the task and how many files or other resources I have to mange.
An IDE basically is a tool (more specifically a collection of tools), and like any other tool the main benefit is making some job easier.
If I am just prototyping, particularly in JS and HTML since they run so easily in the browser with no complication required (but basically true for any language that can execute with compilation like Python or lisp) I almost never use an IDE and instead stick to just a text editor (TextMate, Sublime, TextWrangler for example if you're on a Mac).
IDEs come in handy when you are working on complex projects that might may require compiling code into machine code for example (C based languages) or when you are dealing with complex build parameters like external libraries to load or assets that need to be included in the resulting binary. IDEs usually have steam lined set ups to make these tasks easier.
Additionally in large code bases there are other nice frills, like auto completion of variable names and functions which save you typing or the ability to search for a specific function by reference instead of doing just a text search (this is VERY useful when you have some function called something generic like "GetText()" and you want to find a specific use of it and not every single time any function by that name is used).
To answer the question in regard to my working life, I always use IDEs. It makes things easier because everyone on the team is using the same tools to build the app and I like all the time savers.
In the past few years I have mostly used Eclipse, Flash builder (which is just a custom version of Eclipse), IntelliJ, and most recently the version of MonoDevelop that comes packaged with unity. I'd like to use Visual Studio since I'm working in C#, but alas...Macs.
Some people at work however do work in VI/VIM for example. No one stops them. That may not be true of all work environments however.
If you do server side programmer directly on the machine for debugging purposes you will likely not have access to an IDE (without additional set up) since you will be remotely logged in and in those situations I have used VIM or other unixed based text editors.