The sound of the hf3 headset might take a little getting used to if you're migrating across from just about any other brand of earphones. As Riyad said of the hf2s way back in 2008, fans of bass emphasis need not apply, but that's not a criticism. Where the hf3s success lies is in delivering a clear, detailed and uncoloured reproduction.
Unlike the lower-end Etymotic MC5 earphones, we didn't find that the hf3s lacked presence. It's only if you can't get a good fit that the hf3 headset completely lacks bass; once you get a good seal their low-end comes through and balances out the overall sound nicely. It's also worth noting that the hf3s handle complex music without getting muddied or crowded, and don't show any discernable distortion even at too-high volumes.
It's the high-end that we find the hf3s accuracy really pays off. Female vocals are presented with a pleasantly natural tone, and cymbals ring out clearly and brightly, but without any sibilance to ruin the crisp reproduction. Quite what it is about the hf3s that makes their strive towards accuracy sound good, while the MC5s sound clinical we couldn't say, but whatever it is, it works.
That said, we couldn't find any difference between the hf2 and hf3 headsets in terms of sound quality, which makes us wonder why the newer set is £30 more expensive. Other than volume controls on the in-line remote we're not sure there's anything to justify the price increase, which makes us wonder why you wouldn't just pick up the hf2 headset as it can be found for under £70 - practically half the price of the hf3.
It's under no dispute that the hf3 headset does a great job of reproducing a detailed, uncoloured and, above all, accurate sound. And the provision of volume controls, in addition to the play/pause button and microphone the predeceasing hf2 headset offered is definitely a useful improvement. Inexplicable, however, is the disparity in price between the hf2 and hf3 headsets given how minor the change is - the former offers much better value for money.