I've been watching this thread over the past couple of days and a little surprised about the lack of replies. I was hoping to hear more comments about these courses, but I think people simply have not had much opportunity to see them.
As a member of Eastward Ho!, I feel very fortunate to have the opportunity to play several of these courses as part of an off-season reciprocal arrangement. (For what it's worth, the comment about our season being short may have been tongue-in-cheek, but at the Ho, we keep our regular greens in play year-round, with two holes cut in the winter - the course actually gets a significant amount of play Dec-Mar.)
Both Eastward Ho! and Hyannisport are very short courses by today's standards (at 6218 and approx. 6400 from the tips respectively). Eastward Ho! sits on the waters of Pleasant Bay, abutting the Atlantic, and Hyannisport is on marshland abutting Nantucket Sound. As a result, both courses can be extremely wind-whipped, have some very hilly terrain, and have small but interesting green complexes that can be very challenging, particularly in those windy conditions. I can say with all candor that I will never tire of playing my home course due to the variety of conditions and different lies found in the undulating fairways (and rough).
Oyster Harbors is a different course than these two, as it has a much more "parkland" feel to it than the others. It is a fine Ross design, is always in top condition, and fun to play, particularly for someone who is constantly battling the seaside wind and likes a bit of a parkland respite once in a while.
All three of these courses tend to be more seasonal courses, since many of our members are only here in the summer. Also, the membership wating lists are soooo long (if they even take new applications) that the bulk of the members are in their 70's and older (perhaps lending credibility to the exculsivity theory, Tom). As a result, there is not a great deal of outside play from the younger generations.
In any event, I would love to hear other comments about the area, particularly the Cape Cod courses. (While Kittansett is on Buzzards Bay, it is in Marion, which is about a 25 minute drive from the nearest bridge leading onto Cape Cod.) As many who have commented before at GCA, it is a fine course, but if you every have the opportunity to play Hyannisport or Eastward Ho!, I recommend you jump at the opportunity, no matter what the season.