Interesting question. It's strange that nobody hasn't provided any examples yet. I'm writing this comment a few hours later after having read the post. I expected some fans to post comments like these: "Linux is perfect, it can do everything I need", "I am fond of Vim. Not only it is a good text editor, it can also play chess with you" and so on.

But from the other hand I think nobody could say that some software is flawless. In "The Mythical man-month" by Frederick Brooks it is said: "... the programmer delivers satisfaction of a user need rather than any tangible product. And both the actual need and the user's perception of that need will change as programs are built, tested, and used". I understand it as follows. Once you started using a good program it fits you well. It has all the necessary functionality you lacked before. After some time you get used to the program and start willing it to have more features because "the perception of your need" has changed.

For example, suppose you want to write C++ source code. You start typing it in Windows notepad. It is perfectly capabale because it is intended for writing text! Having written some lines of code you get frustrated - there is no auto indentation and it's very inconvenient to do it manually. So you move to Notepad++ (for instance). Great! It auto-indents the text and, more over, it has syntax highlighting. Hardly anything exists better than it!

With the code growing its getting awkward to navigate it by mouse scrolling or pressing "Page Up"/"Page down". You need some code navigation tool (Does anybody know if Notepad++ has the one?). You switch to another editor.

Then you will want to split the code in multiple files and manage them, compile it, execute, debug, refactor and so on. So you will end up with an IDE. Having started with simple text writing and a small program the evolution of your needs has led you to complex software with a wide variety of functions. And by no means it's going to satisfy you fully for a very long period of time.