I don't specifically insure my gear beyond what is in my home property plan and my travel/holiday insurance. However, I do have DAN insurance (Bronze Pro), for medical insurance in specific dive-related circumstances, and that actually covers equipment lost in e.g. a rescue situation where you need to dump your own and the injured diver's gear (up to a maximum cost). An unlikely situation, but I think that makes for pretty full coverage. As said elsewhere in the thread, how likely is it to loose all you gear while diving? Sure, you might loose a mask or a set of fins, but beyond that?
So basically, that makes for only a few scenarios where it is likely that you can loose gear: stolen from home/hotel room/car (property or travel insurance), in transit while travelling (travel insurance), or, pretty unlikely, in a rescue scenario (DAN).
So no, taking out a specific equipment insurance is probably not worth it, IMO.