I had written this long post (oops, this one turned out too long as well)_ about my experience with ferro cement, but I lost it - I guess it was so long that I had to re-log on, and I lost it in the process - lucky for you guys.
Anyway, I had a 32' Sampson designed gaff-rigged cutter built by a wonderful guy, Jean Claude (most people called him JC), on his home island of Mauritius. She was built in 1979, and except for work on the standing, and running rigging - because JC made a stop in Tortola, and found his new home - got married and had a beautiful child, and the boat sat in the mangroves, somewhat neglected - but otherwise, she was in great shape.
I bought her, "Bonne Esperance" for $6000, and sailed her hard for nearly 2 years, made some minor improvements, and sold her for $12,500 right after Hurricane Marilyn - I wasn't planning on selling her, although I knew I wanted a boat that was a little more....nimble, but he made me an offer I couldn't refuse.
I have nothing but positive things to say about ferro cement - because my experience was so good, and because she was built very well by the guy I bought it from. Tough as nails, and with the wooden mast, long bow sprit that was rusting, sending some rust streaks down her sides, she was often admired - I think because it made people think of either a pirate ship, or Popeye, I'm not sure which. Frequently, people would get off their beautiful "million dollar yachts" (anything that was new, shiny, and big), and dingy on over to talk about my boat.
I got slammed a bunch of times in anchorages, mostly in Great Harbour, Jost Van Dyke, because back then, there were no mooring balls. One time a Beneteau 501 slammed so hard that it cracked their fiberglass, and crunched a stanchion, but "Bonne Esperance" received nary a scratch.
I think the advice from many of the posters, that surely know more than I, to get someone that knows FC boats to look her over. The only thing I can think of which could be bad, is if the steel meshing that's used to build these boats, if that got wet, rusty, that would be a bad thing (duh, right?).
Good luck, and smooth sailing