Well, I do know that they've had massive issues with their new manufacturing process in general... as it's completely dissimilar to the process they'd used previously for any new airplane. The emphasis has been on selling jobs, and little else. There have been employees who have gone to the union as well as the FAA with concerns that jobs are being bought off as completed, when they're anything but. There's some actual concern regarding safety.
Everything about this airplane has been a massive rush to get it done and reach manufacturing benchmarks, regardless of the actual progress made. One good example is the initial roll-out of the airplane a few years ago. That airplane, when it was rolled out... had no floors. No wiring. The doors were painted plastic plugs held in place by temporary wood framing. It's been some really stupid blunders, as well. Things as simple as the sequence of events. They had one of the fuselage tubes in a sling to get it off the ground, and were in a rush to install the floor of the airplane. Well, composite did what it does, and flexed as they had the tube suspended. The floor pieces were then the wrong length, but adjusted to work. So then when the tube comes back down, it's now permanently deformed. Crap like that.
Boeing currently has runway 11/29 closed at PAE, and has been using it as a parking lot for 787 shells for a couple of years now. They assembled the basic chassis of many airplanes with no real path to completion, rolled them out and have stored these new airplanes outside for over a year now. As they have made significant changes to the manufacturing process of the airplane, each of these will have to be brought back inside to be completely ripped apart and re-manufactured. As I flew over it a while back, I counted upwards of 25 airplanes sitting outside all around the airport. They've literally run out of places to put them, because they won't stop producing new ones to fix the catastrophe they've created.
They've also had some issues with just manufacturing skill. They've been hiring assembly mechanics who have little (if any) knowledge regarding anything mechanical. They've been running training classes to try to teach people how to drill precision holes in composites, which hasn't exactly worked, and the result is a huge number of over-sized holes and fasteners. Basically, just shoddy workmanship.
Edit: I'm not saying that it's a crap airplane, or that they're all unsafe... nothing like that. It's just that this airplane has suffered from severe and extended manufacturing problems. I'm confident that what Boeing delivers will be safe, I just think it's going to be a very long time before they've sorted out how to competently make one of these airplanes. In short, they should have stuck with the manufacturing process they used on the 777. Awesome airplane, and compared to the current situation, an absolute breeze to design and deliver.