Starting big project / first WP application with lots of custom coding

Hey everyone!

I'm investigating migrating an existing web project to Wordpress 3. The website in question is built with a custom CMS we did some time ago.

Our client, among other things, offers courses and professional education tracks, for which we have built an extensive PHP app, that co-exists with the CMS. PHP5 OOP, Smarty templating, admin area, public area and live XML feeds. Lots of different classes, lots of conditionals for fetching just the right remote XML info (don't get me started on the supplier's datastructure!) via cURL. (With WP, we can ditch cURL, I've read.)

For all the obvious reasons, we would like to switch to WP and usually, when learning a new system, we undertake a project that seems ludicrous at first. You know, to get the blood flowing.

My questions are rather vague and broad, perhaps: what do I need to look out for? How do I get up to speed as quickly as possible on programming with WP.

Any pitfalls? What books/videos/courses do you recommend to get down with plugin development? Any specific RTFMs? Any groups, forums to join and follow?

Basically, I think, I want to use WP as a development framework. I'm proficitent enough with CodeIgniter and ExpressionEngine, besides doing custom PHP projects for the last 10 years or so, so I'm not afraid of diving in deep.

I'm reading up on stuff in the Codex in a big hurry, have the Devlounge "How to write a plugin" closeby, lynda.com at hand and soaking in anything I can find.

I really appreciate any thoughts, comments and "don't do that!"s. :slight_smile:

Thanks!... Nico