The HF5 is my second pair of Etymotics and I must say they have proved disappointing. The previous pair, in which one side failed with no repair option, worked much better.
The noise attenuation was more effective such that I could hear music well at highway speeds. With the HF5's, the output is hashed at 30 MPH.
From Etymotic, I obtained the larger foam earseals, which help some. So does a balaclava to reduce noise and solve one other problem: these are longer and stick out more so when you put your helmet odd, it tends to dislodge one or both earbuds.
Bottom line? Not sure I would buy them again, although I'm trying other things to improve performance. (Posted on 12/8/12)