I've been toying with an amazing new web analytics tool called ClickTale. It tracks everything a user does as they interact with your site, so as well as the usual heat maps and the like, you can actually observe a user's mouse moving around, clicks, typing, the lot! Amazing, but somewhat scary. Certainly could give some insights into how your users interact with your site, particularly complex elements like forms.
Here's a video of me testing it out to demonstrate quite how detailed it is. Wow!