I like VNC for work within my own LAN, but for WAN work I've had better luck with logmein. Most equipment comes with firmware that is configurable for use with the VNC protocol, but many of them require you to 'turn on' or 'unblock' VNC traffic. I'm usually able to get port forwarding and TCP/IP settings rigged up to use the service, but as stated above, it's different wherever you go.
VNC has saved my father's butt several times. I live 30 minutes from him, and more than once he's called me with the "what's this message I keep getting" question that I've been able to answer pretty quickly by remoting in to his computer.
I use VNC to tweak settings on my cab from my laptop. Really makes things nice -- no need for a local keyboard or mouse for most work. Not to mention I can work on most of my settings right from my couch upstairs, allowing me to be sitting next to my wife, giving her the illusion that she's getting some 'quality time' with me.
