- in what respect? I find it very powerful, esp when it comes to assigning rights to groups and users that also exist on your Windows network. Its flexibility is mainly visible from the "other" side - i.e. when you're logged on to a Win network.
Also, VNC (I use the free version of RealVNC, there are other flavors that essentially do the same thing) can be secured by letting it accept only connections from the local machine, and opening an encrypted tunnel between the two boxes that you want to connect. Like this:
VNC Client <--> localhost...[SSH tunnel]...remote host <--> VNC Server