This is a great GUI system, I have a few questions about what to expect when using it though.
Thanks

I'll do my best to answer your questions.
I am trying to build a gui system for an Ogre based application. I took a quick look through the api reference but I couldn't find any manual docs or tutorial examples - will these be released soon?
All I'm going to say about this is "hopefully". The first set of additional documentation will accompany the Beta-1 release that I'm struggling with at the moment. Every time I try and be more specific as to when the release will be made, something happens and I miss the target date by large amounts (I had originally said June, but you're all still waiting)

Also, how do you recommend I tackle drawing primatives like lines, curves, and basic filled shapes inside a canvas type widget?
The best way would be to render those items onto a texture externally (maybe using Ogre for example), and then use the resulting texture as the basis for a Gui 'imageset' that can be used to put imagery onto UI elements.
How is resizing handled? Can I use fixed pixel placement relative to edges?
Metrics can be specified as relative or absolute (pixels).
(such as, keep a close button exactly 10 pixels from the right edge, etc)
Right edge and bottom edge alignment are on the TODO list, at the moment it's all based on the top and left edges.
Will I have to recode a lot of custom widgets I make?
Recode? I'm not sure I understand the question. If you mean do you have to code widgets to change thier appearance, it depends on exactly what you need to achieve.
I hope these aren't too redundant of questions, I tried to search but found nothing on tutorials and such.
Not at all

The forums are still relatively young, so they're still building up a useful archive of information.
Hopefully I've addressed your questions, if you need more elaborate or in-depth answers, let me know which areas you need explaining
CE.