Actually... I've had Linux servers for over 5 years now (I think I have my 6th server now, always building new pcs from parts eh) and I didn't use any monitor, keyboard or mouse for 4 years. I got a KVM switch last year, but before that time, it was just a tower with a powercord and some ethernet cables....

This always worked fine. I always set my BIOS not to halt on any error.

Using your LAN, controlling the computer through VNC and SSH is done easily. The Linux VNCserver (XVNC) is really really fast. Just install some lightweight windowmanager (I use IceWM) and let your VNC server start that on startup. Works like a charm!