I have watched gullets being built at Fethiye in Turkey, and they seem to be put together in time honoured way. They use softwood, some sort of pine, and I would be worried about teredo worm, which is bad enough in hardwood boats. They are caulked again in the time honoured way, and if done well I would suppose they would be quite watertight for years. However, put a gullet into a force 10, and I would not know quite how good a sea boat they are. Most of the ones I have seen are being motored around, and rarely do you see a Gullet in Fethiye which is sailing using a full compliment of sails. I have dived under them and they do not have a pronounced keel in the same sort of way as some traditional old wooden boats in the UK - eg Cornish Trawlers, Prawners etc. I assume that they would not point very well into the wind. On balance I think I would invest my hard earned pounds in something less prone to worm, with a better deep sea profile
Having spent a couple of weeks on one on a holiday a few years ago, I remember that the movement in any sort of sea was pretty nauseating and rolly. We were out in about a 2 metre swell. ( and I have a farily stong stomach) They are pretty shallow and flat bottomed.
<hr width=100% size=1>Life's too short- do it now.
There have been a considerable number of threads over the years about gulets, for example <A target="_blank" HREF=http://www.ybw.com/cgi-bin/forums/showthreaded.pl?Cat=&Board=LIVEABOARD&Number=391778>HERE</A>. The concensus seems to be that they sail badly and not suitable for open sea passages, but are attractive and comfortable for living aboard.
I'm attracted by an Egyptian felucca, but the reality is that while these are perfectly adapted to sailing the Nile, they would be quite hopeless around Britain.