I'll weigh in with a few thoughts, if only because I've spent a lot of time reading about, and talking with golfers here in Wisconsin about, the Kohler courses.
First of all, I've long believed that the success of Kohler as a golf destination has a clear link to Kohler as a businessman. He's made a fortune out of a pretty mundane thing -- toilets and bathroom/kitchen fixtures. He's not the first person to do so (making money off the mundane), but the Kohler line of products is known in the industry for their high quality, look, and high-brow reputation they bring -- which is something one can say about the Kohler courses, as well. I think Kohler took his model of the business he was familiar with, and applied it to golf -- after all, there are a lot of mundane golf courses.
Certainly he realized the geographic importance of Sheboygan -- maybe not the center of the universe, but an easy drive (Kohler, essentially a company town/bedroom suburb of Sheboygan, is a stone's throw from a major four-lane interstate highway) from Milwaukee, not that far from Chicago, Madison, and the Oshkosh/Appleton/Green Bary corridor, and a pretty easy day trip from the Twin Cities. Heck, it's a lot easier to get to Kohler from Milwaukee or Chicago than to drive from either of those two metro areas to Lawsonia.
I think it's fun to speculate about a Bandon model of different architects for Kohler, but I sense that he and Dye had such a unique relationship that Dye was able to do what I might call "variations on a theme" with the four courses. (The long-rumored story about the Straits is that Kohler and Dye played Ballybunion -- the old course, not the Jones version -- and he told Dye, this is what I want on the shores of Lake Michigan. To Kohler's credit, he invested alot of time playing courses in Scotland and Ireland, sometimes with Dye, before launching his golf courses.) Make no mistake -- Kohler built the Straits with the direct intent of luring the kinds of tournaments it has (PGAs, Ryder Cups, USGA events). He built the River and Meadow Valleys clubs largely because a bunch of guests at the resort (which is a pretty nice place) wanted to golf, and Kohler had nothing to offer them (he even approached a local country club to buy them out, but was turned down.)
And, as others have pointed out, relative to the regional competition, the Kohler courses are pretty strong -- certainly much better than any other publics in Wisconsin at the time they were built (save for Lawsonia), and arguably as good/better than what you'd find in the Chicago or Twin Cities. And Kohler's timing was good -- he opened the four courses over a period of a few years in the late 1980s/early 1990s, which was a pretty healthy time economically.
I do think the economic downturn will hurt business there, but it's hurting all golf courses, and Kohler has the money to ride this out. The Straits is hosting three major, major events in the next decade (two PGAs, a Ryder Cup), and that can't hurt business, either.