If the VNC server is on a UNIX-like Free Software operating system (where per user licensing fees are non-existent), VNC works more like a Citrix/MS Terminal Server add-on (if you are familiar with those two applications from the W32 world). However, due to the proprietary nature of W32, the VNC designers couldn't do much for the W32 fans of VNC except create something that works like PC Anywhere.
VNC is a very simple application and can be made to work on a palm pilot, a win ce device, or even on a microwave oven--it's easier to create a VNC client than try to squeeze W32 or X into most consumer devices.
Another plus is VNC can use any encryption tunnel you care to throw at it. If you upgrade the tunnel, VNC gains the advantage right away without recompile or waiting for a upgrade.
If you install a Linux-based office suite on a central server and use VNC to service a local network of less powerful desktops--you can tell your MCSE friends what Zero Administration is all about.
This software uses TCP/IP or any protocol you care to enhance it to support. This means if you know how to hack it (and you probably do--VNC is simple) you can get your kids to turn the lights on and off in your home from a computer at Disney Land.
VNC is GPLed and comes with full source code (executable servers and clients are also available free of cost). It is not shareware. There will never be a price tacked on to the server or client. It is provided by a research group recently acquired by AT&T Research Laboratory in United Kingdom. Visit www.uk.research.att.com and follow the links to the VNC site.
You will probably want to use VNC if you'd like to add a few more years of usefulness to some of the older computers you administer at a computer lab or small business LAN and improve the quality of life for your computer users.
It is also a great way to upgrade all the softwares, RAM and storage capabilities on tens (if not hundreds) of PCs by upgrading only one server (you don't have to change the client PCs' operating system in any way to benefit from this upgrade--just add a VNC client--it would be preferable if you install an open source operating system like Linux or FreeBSD on the server however to support many clients).
If you have customers who uses a computing solution you sell you may add VNC to the solution without cost or expensive licensing obligations to the community responsible for the creation and maintainance of VNC. This is true no matter where the customer's installation is in the world.
The only cost is your consultation time and you are always welcome to charge your clients for that cost. If you hire programmers to add to VNC you may wish to send the enhancement back to VNC and that is always welcomed.
Another excellent way to make your applications available to many people around the world is to use the world wide web infrastructure. The interface is universal. There's arguably even less administration. And again you can increase the capability of the server by utilizing web/security/client-server savvy operating system from the open source world. See database-backed websites.