Geany is excellent. It’s a lightweight programmer’s editor with enough features and configurable hooks to provide the important parts of a full-blown IDE. It renders text clearly, never feels laggy, and doesn’t get greedy with your RAM. I recommend it to people who can’t stand the bloat that’s often seen elsewhere these days, but would rather have a GUI than resort to vim.

A couple minor annoyances to me:

• It doesn’t yet support the Language Server Protocol, so any language that it doesn’t understand will be left without syntax and context-sensitive features. (On the other hand, it does support a lot of languages.)
• It inherits Scintilla’s use of Gtk for its GUI, so it’s an alien app on Qt-based desktops.

I use it anyway, because I find it easier / more comfortable to use than Kate.