Summary: I have put the W4 through its paces, and after the first round of extensive testing, here are my impressions.
My main reason for getting the W4 is to hopefully replace the SE535 and W3, since I find them too colored or fatiguing/bright without EQ.
Pros: Great fit, nice cable, pleasant sonic signature (non-fatiguing)
Cons: upper/mid bass still bloated, sub-bass not enough, not enough air
Summary: I bought these as an upgrade from the W3, which while extremely fun, I soon became disappointed in, due to mid bass bleed into the midrange. This caused vocals to become too chesty and distortion rock guitar notes too rounded instead of hard edged. Enter the W4.
Summary: *I listened to the Westone 4Rs using iPhone 4S and the latest iPod Classic (6th Generation). The below sums up my listening experience from these sources only.*
The Westone 4Rs fit my ears better than any other earphones.
Summary: So when I got the earphones my expactations where really high. These were to be my best and last earphones I'll have but it didn't happen. Overall the sound is warm and smooth . It is balanced and nothing really jumps out at you.