The problem with text boxes is the determination of the cursor position, and the coordinates of areas around highlighted text. There are ways to compute this information with a CustomElement. We have been asked for a vector text box many times, so some basic version must be in the standard distribution.
The other types of UI elements mentioned by Lazarus are fairly easy to implement in the current VG.net release. Our plan is to provide non-graphical base classes, in the form of source code and binaries, for these basic UI elements, as well as derived classes demonstrating how to create your own visual look.
When I say non-graphical base class, I mean a Picture containing logic, but no Elements. Elements within the Picture will be retrieved by name by the base class or by virtual properties. By overriding properties your derived class can plug in the Elements needed by the base class -- you can design the derived class in the designer.
Justin has lots of experience developing advanced UI libraries using VG.net. His proposed UI library has complex controls and lots of properties that go beyond the basic ones planned for the standard VG.net distribution. Justin, I can put a screen shot on our site if you wish to add one to this thread.
The layout and keyboard focus Justin mentions are important features, but neither feature is strictly necessary for the basic controls mentioned by Lazarus.