If the GUI is a subset or 1:1 feature match to the CLI, then I'm happy. If the GUI is superior to the CLI in what system features it can work with, then we've got some serious problems and I will pout in the corner until the vendor makes all features that are available through the GUI also be available in the same capacity within a CLI.
Ideally, a GUI should simply be a web front end to the existing CLI/API interface. Witness Microsoft Exchange and the Exchange Management Console being, in essence, a pretty face to the Exchange Management Shell.
