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Pros
Pro Does not require a rooted phone
GNURoot is a completely self-contained app that cleanly uninstalls and doesn't need root permissions.
Pro Includes a VNC client for GUI apps
Setting it up takes some effort. And 3rd-party VNC client (or X server) apps might have a better user interface than GNURoot's default. These also work, but also take some effort to set up.
Cons
Con Wakelocks on by default
It drains the battery pretty quickly when running.
Con Requires a lot of manual configuration
GNURoot doesn't hold your hand and isn't even documented very well. Getting anything graphical to run takes some doing.