I only began using them recently but I've had pretty good luck with them. They're designed to sink fast, but in deep fast water you'll want add additional weight.
When fishing nymphs in general, not just with this pattern, you want enough weight to get deep where the fish are. This means that you'll get hung up the rocks occasionally. That's normal. But if you are getting hung up really often than you are using too much weight, so you use less.
The ideal thing is to get a deep drift, but not get hung up too often. It takes practice.