I switched to HF5s last March. Mixed bag: the sound isn't as "dynamic" as the ER6is and sounds a bit more flat. I'm sure it's much more accurate, but my ears are used to loudness compensation of music, especially when moving. Even mowing the lawn I prefer a little more high and low end. The ER6is sounded better to my ears because of this. The cords on the HF5s is much thicker than on the ER6is (which was their Achilles heel - BTDT), but works OK on a bike. They also stock out of my ears about a mm more than the ER6is, but again work OK in my helmets.
I also have a pair of $35 Sonys I bought around the same time. They are somewhat brighter, but not as smooth. They also block almost as much sound and the cords are thinner. Much cheaper so they are a decent option.
I miss my ER6is. My wife won't let me have hers.