I don't love the ER4...yet!
I don't have much experience with IEM, I have been using a pair of IE8 in the last couple of years at work and while commuting connected to my iPhone. Unfortunately by baby literally chewed them so I had to find a replacement.
I got some ER4S today...first impression: they obviously isolate much better (and this is one of the reason I chose the etymotics) but the sound through my iPhone is a bit dull.
They sound very different, my ears got used to the IE8 signature, so rich and warm, so probably I need some time to "adjust" them.
The 3 flanges tip seems quite comfortable, but, honestly, I have no idea how deep I'll have to push it in the ear canal. So basically I'm not sure I've inserted them properly.
I'll be using them at work with a E7..hope will be enough, but tonight I'll give them a try in my main rig, connected to to the WA3 and Havana.