I bounce about between Mac, Windows and Ubuntu and while Emacs used to be my editor of choice, I'm finding that in my old age I prefer to something GUI-based (using command-line for the shell is still fine by me). My preferred editor is Komodo Edit, which the advantages of:
- Being free (as in beer)
- Available for Mac, Windows and Linux
- Syntax highlighting for a boatload of languages, including C++ and PHP (I'm using it for Ruby, Python and PHP myself)
- Code completion, even for classes I defined myself
- Ability to "remote save" via FTP, SFTP or SCP
- Support for organizing your files into projects
- Tabs and other interface niceties
I'm not sure how lightweight it is, but it certainly feels snappier than Eclipse!