Never had a problem when my hyperlite asym tarp was pitched correctly.
Once I was in a hurry and got the tarp up backwards. Some water dripped in before I realized what the problem was and quickly flipped the tarp side for side.
I used the poncho/tarp for a while. It leaked at the seam. All I had to do was alter the position of the seam to the other side of the ridge line so the felled edge faced down instead of up. That's the way shingles work too. If there'd been a wind strong enough to blow water up the slope of the tarp, I think it would have continued to leak.
Other than those two instances, I've never gotten a drop in the hammock.
A word of advice. Never hang on a ridge top during a storm. The few people I know who've done that in high winds have gotten wet.