I agree with Austin. The rest of you saying it's not worth it are possibly going to be eating your words in time. .xxx domains are going to be hot for adult companies, especially if you get a good one or two word short domain. People who sit around and wait for things to happen are always the ones that lose out. Take a risk, throw $500 or $1000 bucks at a handful of domains and see what happens. Worst case you loose a grand and you call it a day, best case you flip the domain(s) for $10k a pop and you make yourself some money. You obviously have thought about it because you posted about it so take a chance.
Keep in mind some people are going to tell you it's not worth it because they are on the registrars website right now searching for hot .xxx domain names. Don't be a fool, follow your gut decision and go from there. Spend what you can afford to loose and you might make some cash from it.
Brian