Consider this:
Monitors/resolutions these days are pretty huge. I have two, my big one is at 1600px wide, and there are plenty monitors out there with even higher resolutions. Websites that extend over all that are really hard to read, you almost have to turn your head to follow a line of text. And, if your wrapper extends, everything inside kind of has to follow along, too, or you run into layout problems. I'm not saying it's not doable, it's just not my preference. And since I prefer my sites with a set width, I have no experience with fluid ones.
With the middle image issue, I assume you're referring to our problem with losing the transparency when adding the background color which we need to fill in under it, right? Yeah, I don't have anything on that yet, either. Let me ask the experts.