I don't have any personal experience owning a 30 foot Seafarer yet, but I owned a 1983 Seafarer 23 that was a McCurdy and Rhodes design. We absolutely loved that boat. It was very stable reasonably fast and well layed out to our thinking. The construction seemed pretty good compaired to most of the production boats that I work on.
They made three completely different 30 models, the most common is the McCurdy and Rhodes designed Swiftsure. They were apparently made from the mid seventies until they stopped production in 85. As near as I can remember the other popular boat from the sixties was a Bill Tripp design and was a good sailor, well built and stunning Eye Candy to my way of thinking. The other was the 30R I am not sure who designed it, but it looks like a little different Tripp design to me. I am told that the R stood for racing version although I haven't been able to confirm that information. I spent the day on one of these several years ago and was pretty impressed with how well it was put together.
I just sold my Morgan and am currently looking for a late model Seafarer, although we haven't decided whether we want a 26 or a 30. I want the smaller boat for ease of handling and the wife wants the bigger boat for more room.
Assuming that you are looking at one of the later model thirties, make certain that you take a close look at the rudder. The bracket at the bottom ofthe rudder is bad about breaking due to electrolisis. The only other thing is that they have an interior liner that makes it a bit tough to mount anythying on the deck and make rewiring something of a pain. The other side of that is that it is a breeze to keep clean.
Good luck on your search