I've been selling on Local Bitcoins for months now and have had very little trouble, barring the occasional time when my coins have been tied up overnight while banks carried out security checks.

It seems to me that this is an argument for not accepting payment types that can be cancelled so easily, and also for only dealing with people who have reputation to lose. There are plenty of new features, and promised ones forthcoming, to make it easier to avoid accepting a deal with someone you'd rather not deal with.