It's not perfect, but it's pretty good.
There are a lot of little things that could make it better that add up over time, like having more voices than just one, and having ending animations in all forms of clothes, but this is a simple animation viewer, and you shouldn't expect more than that. The fact that it lets you adjust speed and whether the moans are synced is pretty good, and it's straightforwardness is very welcomed. 

Also, it's free, so really what more do you expect ? Dev owes you nothing, and you still get this. for free. just take it. If you got complaints, YOU do something about it, dangit.