First let me start by congratulate Thunderbax for his innovative plugin "Admin custom page". It really helps expanding the admin backend a lot.
It is a good plugin, but it needs improvements the way I see it:
It is good that one can create a custom page, but it would be lightyears better if one could create more pages as one need 'em. It would also be really good if one could use the WYSIWYG editor instead of using html to build the pages.
Apart from these suggestions I'm pleased with the plugin.