I have the Leviathan pack. I wouldn't exactly call it high quality, and I don't think it's worth the full price. Many of the samples are clipped (which makes absolutely no sense in a sample pack IMO) to the point of sounding distorted, and have weird phasing issues. The cymbals especially are mostly awful. Some sounds actually end in non-zero samples, resulting in clicks (see attached picture) - makes me wonder if they even listened to what they made. Also, the loops are a joke.
Having said all that, there are lots of good drum and percussion samples in the pack as well, and probably many useful FX samples. The free sampler gives a good idea of what to expect, so you should definitely try that.
E: word choice
