As yshuditelu's answer and TheTXI's comment indicate, polls aren't universally popular. However, I don't think they're going away - so I think it does make sense to support them better. I do agree that it's not the primary goal of any of the sites, but they can occasionally be handy - and I think that the more diverse the range of sites gets (with SE particularly) the more cases there'll be where polls do fit in well.
I believe they should be a separate question type - and in the "Questions" tab, one could include or exclude poll questions. That way those of us who aren't keen on polls never have to see them, and those who do like them get a better experience.
The options for a poll question (after it's been asked) would be:
- Vote (only up?) for a particular option
- Add a new option
- Add a comment to an option
I would probably suggest that options should be restricted to a single line with no mark-up: if you want to provide justifications etc, use comments.
This could be displayed nice and easily with bars etc by each option - have a "results summary" just below the question, and then the expanded versions with actual scores and comments underneath.