SciTE is a powerful programmer's editor and Notepad replacement based on the popular open-source Scintilla (a component used within many other editing tools).

You don't need to be a developer to use the program. It looks much like Notepad, so at a minimum you can just launch it, type some text and save the file, using all the keyboard shortcuts you know already.

It won't take long to notice small benefits. Pressing Ctrl+N creates a new tab, for instance, allowing multiple documents to be open at once. And Ctrl+F gives you a persistent search area at the bottom of the screen, where you can instantly mark all search hits as well as zip through them one-by-one.

Start exploring the program and you'll quickly discover more. Regular expression searches, find across files, drag and drop editing (select some lines, drag and drop them somewhere else), case conversion, bookmarking, session management.

There's also plenty of developer-oriented power, including syntax highlighting, brace handling, code folding, and options to compile and run programs, turning it more into a basic IDE.

Version 3.7.1 Changelog

The Scintilla namespace is no longer applied to struct definitions in Scintilla.h even when SCI_NAMESPACE defined. Client code should not define SCI_NAMESPACE.
Structure names in Scintilla.h without prefixes are deprecated and will now only be usable with INCLUDE_DEPRECATED_FEATURES defined.
Use the newer names with the "Sci_" prefix:
CharacterRange ? Sci_CharacterRange
TextRange ? Sci_TextRange
TextToFind ? Sci_TextToFind
RangeToFormat ? Sci_RangeToFormat
NotifyHeader ? Sci_NotifyHeader
Previously deprecated features SC_CP_DBCS, SCI_SETUSEPALETTE. and SCI_GETUSEPALETTE have been removed and can no longer be used in client code.
Accessibility support allowing screen readers to work added on GTK+ and Cocoa.
Textual tags may be displayed to the right on folded lines with SCI_TOGGLEFOLDSHOWTEXT. This is commonly something like "{ ... }" or "<tr>...</tr>". It is displayed with the STYLE_FOLDDISPLAYTEXT style and may have a box drawn around it with SCI_FOLDDISPLAYTEXTSETSTYLE.
A mouse right-click over the margin may send an SCN_MARGINRIGHTCLICK event. This only occurs when popup menus are turned off. SCI_USEPOPUP now has three states: SC_POPUP_NEVER, SC_POPUP_ALL, or SC_POPUP_TEXT.
INDIC_POINT and INDIC_POINTCHARACTER indicators added to display small arrows underneath positions or characters.
Added alternate appearance for visible tabs which looks like a horizontal line. Controlled with SCI_SETTABDRAWMODE. Feature #1165.
On Cocoa, a modulemap file is included to allow Scintilla to be treated as a module. This makes it easier to use Scintilla from the Swift language.
Baan folder accommodates sections and lexer fixes definition of SCE_BAAN_FUNCDEF.
EDIFACT lexer and folder added. Feature #1166.

Verdict

SciTE isn't the most powerful of programmer's editors, but it's also easier to use than many, and the core editor (Scintilla) is one of the best around. If you're not currently happy with some other Notepad replacement, it's a must-try.