OpenBSD is a minimalist operating system: my full web development setup takes 4GB on disk, and rarely eats more than 4GB of memory.
OpenBSD has everything I need in base: X11, cwm, xterm, tmux, vi, httpd, etc. All those programs are well documented, have consistent APIs, and sane defaults. There is almost nothing to configure.
You can install OpenBSD on bare metal in ten minutes with all 3rd-party packages and personal data restored from the latest backup.
You should try it out.