Agile Toolkit delivers simplicity on top of very powerful code-base. Many things you can think of are probably have been already implemented on Agile Toolkit
If you have any question on how to do something with Agile Toolkit, ask it on Stack Overflow with atk4 as a tag.
Your software will continue to be compatible with 4.0.x releases of Agile Toolkit. With minor changes you can also upgrade to 4.1.x. You can get newer version from here: http://agiletoolkit.org/download.
When doing upgrade, replace your current "atk4" directory with the newer release.
Documentation located on http://agiletoolkit.org/doc is aimed at 4.1 branch of Agile Toolkit. Refer to http://agiletoolkit.org/whatsnew for the differences between versions.
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