I agree with you to be honest. Some things could have been implemented in a simpler and cleaner way.
I am making some changes (fixes and improvements) to P2 that I want to release later on. Since you've already done the categories bit, would you mind to send me the code?
You can find my contacts here: http://neminis.org/about-vincenzo-russo-nemo/
PS: for the record, this is the plan:
* fix the post title permalinks [done]
* adding the title to the post form, edit form, and a backend option to enable/disable this facility [almost done]
* adding the categories to the post form and a backend option to enable/disable this facility
* adding a backend option to choose if you want the threads closed by default
* minor changes to the css [done]
* support for threaded comments
* changing the behavior of posting comments: when click 'reply', the comments form will be shown right below the post, not below all the comments. After posting the comment, the comment will be added at the end of the comment list and the page will be scrolled down there.