Second, no, we didn't suffer any damage. We spent several hours preparing Sea Gem for the worst (removing canvas, adding fenders and lines, etc), and the result is that Sea Gem was, if anything, over-prepared when the worst never arrived. Some of our neighbors lost their canvas awnings because they did not remove them in advance, and one of our neighbors suffered some serious deck damage: a cleat pulled right out of the deck, leaving a hole behind. Torn canvas is, of course, easily avoidable by removing the canvas before the storm hits. The disappearing cleat was likely more an issue with poor boat construction than anything else, but that can be mitigating by using dock lines with more "stretch" and not tying more than one line to a single cleat to spread the load.
We were actually more afraid of damaging the marina's property than our own. Based on where the strongest winds were coming from, we knew that we would be putting a lot of strain on a single wooden piling that we were tied to. Breaking the piling was thus a real possibility and would have been expensive to repair. Fortunately, the piling held strong and both Sea Gem and our wallet escaped Isaac unscathed.
Well, probably sort of. Isaac might have destroyed our GPS antenna, which was not working when we went sailing last weekend, our first sail after the storm passed. The antenna was old and the timing of its passing could have just been a coincidence, but I do know that it worked before Isaac and was not working after Isaac. Fortunately, the replacement cost only $25, and so determining blame does not merit any effort: we won't be filing any insurance claims this time around.