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Full user review
"One of the most broadly useful utilities around"
You can poke around inside any type of file, any language, with tons of macros. Has some IDE functionality. Great for writing scripts. Lightweight.
It's not as good as a full-on language-specific IDE for development.
This is one of the first things I install on any computer. It is useful for looking into any type of file, and is much much powerful than traditional notepad text editors.