Vim is the perfect replacement for vi.

Vim includes hypertext help, powerful ctags support, syntax coloring, visual selection, paragraph reformatting, triggered autocommands, and mouse support.

Vim runs on BeOS, every sort of UNIX (including Linux and FreeBSD), microsoft windows95, NT, MSDOS, OS/2, the Macintosh, and the Atari ST. It was originally created for, and still runs on, the Commodore Amiga. There is a port for Acorn RiscOS in the works.