I love how easy ActiveAdmin is to use out of the box, but it can force you into using a panoply of workarounds for forms with any significant level of complexity. The challenge I faced was making this:
Entering the pond
If you don't know already, the framework is dead. That is to say, unless you have money to burn, frameworks like Zend, CakePHP, Django, Struts, .NET, and even Rails should not be considered as a foundation for building anything but the most unique and game changing websites*. The age of the framework for building websites is gone and it has been replaced by the open-source CMS or Content Management System.
I've now been working professionally in Drupal for a year and have learned a lot about it; I have some patches into contrib but I've not really done much with core other than some simpletests I was too shy to commit at Drupalcon and some comments trying to help people out on d.o. Prior to my stint as Drupal programmer I was a hardcore Ruby on Rails developer for about 4 years. Over the last two years in particular I've learned a lot about frameworks and I'd like to share an observation about which framework feels right to me for which situations and why.