All very nice apps, but DameWare is MUCH better than all of them combined. Terminal Services, while a nice feature, has it's drawbacks. For instance, you cannot remote install *some* apps that are MSI based. VNC and RemoteAdmin are slow apps (i.e. screen scrape updates). DameWare can be remotely installed (the agent pushed to the NT-based client/server). Also, you can get additional information about the server (installed software, services, etc.), remote control the command line, manage local user's, and also domain user/group management.
Check it out at
http://www.dameware.com.
Very cheap licensing.