I've been using the Etymotic ER-4 for years and recently just bought the HF5. When I first got the ER-4's years ago, my friends first thought I was crazy for paying $275. But I listen to all my music while commuting on the train. If you loved music as much as I do, would you spend that much on a pair of speakers for your home stereo, or skimp and spend $50?
The ER-4 delivered like no other earphones, with not only the sound quality, but the noise reduction. As someone once said "It's the closest thing there is to injecting the music right into your brain." I completely agree. It took some getting used to 'listening' to the bass as opposed to feeling it, but now these are irreplaceable.
I have bought several pair of the ER-4's due to damage, losing them, etc. And it was time to replace my current pair. I decided to get Etymotics newest model, the HF5. I didn't expect a huge improvement over the ER-4's, but I was wrong.
At first I felt like the earphones didn't fit as well as the ER-4's. But then I realized that these actually go DEEPER into your ears than the ER-4's. And once I got them in there... WOW! The sound was actually so much bigger and brighter than the ER-4's. The ER-4's were great, but the HF5's is like watching High Definition Television compared to regular TV. The highs are brighter and the bass is bigger.
The only thing I wasn't happy with, at first, is the cord. They seem to have switched back to the more grabby rubbery style cord as opposed to the smoother plastic. While the rubbery feels nicer, I was worried it would grab onto my clothes too much. That hasn't been a problem so far.
They could have also included a few extra filters. The filters need to be changed every few months when they get gunked up with earwax. This model only includes one spare, and it would have been great to include more.
Other than that I would say these earphones are superb and worth every penny.