I'm on the road this week, and the subject of reference designs has come up in many discussions with vendors. I happen to be a firm believer in reference designs, as they can take a lot of the guess work out of a design.
As you might expect, there are many definitions of what a reference design is exactly, and most of them are accurate. In most cases, the actual reference design depends on the product being highlighted and the application it's intended for. In some cases, the reference design is simply a processor and some circuitry that goes around it, like particular I/O, or power management, or other processing functions. In other cases, it could be a design that's nearly ready to go to production.
From the designers I've talked to, they take advantage of whatever they can get their hands on from the vendors. So if you're a vendor, I suggest you put some of your best people on this task.
From the vendors I've spoken to, some are already to market with these designs, and some are just getting there. But in most cases, their importance is not lost.