My girlfriend and I both have semi-dry suits and we dive in New England - the only time we have ever been cold was when we did repetive dives in water that was in the low to mid 40's. For us the option made sense since we spent about as much on the semi-dry suits as we would have if we bought a wet suit so that added warmth and reduced water flow through is well worth it.
I would of course love to have a dry suit but I don't really want to break the bank just yet....that will have to wait at least a year or two
