I vote for Qt Creator. It's open source and cross platform (win, linux, mac).
The syntax highlighting is very decent. For example highlighting of a symbol under cursor highlights it correctly inside its scope, not just the same word in the whole editor. Code completion just works (unlike Visual Studio's Intellisense).
I like also small refactoring features, like changing declaration of a method in a header file will automatically sync the change to the implementation in the .cpp file. The code editor has also features like follow symbol (Ctrl+click), find usages, switch between definition and declaration, etc. These things in Qt Creator just work, while in other IDEs I've tried, only work sometimes.
Although the IDE is not as customizable as Visual Studio or Eclipse (forget dockable panels), it's organized quite ergonomically and it's very fast (unlike eg. Eclipse).
It's worth to mention, that the Qt Creator IDE was designed to work with the Qt libraries, which itself is a great cross platform application toolkit for writing any kind of app imaginable. It literally runs everywhere, eg. besides desktop platforms also ARM and embedded platforms, Android, soon iOS. You can of course use Qt Creator and not use the Qt libraries if you don't need them. However if you are into C++ and cross-platform development, I strongly recommend looking into Qt itself.