Pros: Very comfortable, great cable, slick design
Cons: Bass is way too boomy/muddy, upp-mids too bright, treble a bit recessed
I don't like to buy headphones solely based on people's recommendations without auditioning them first, but the reality is, you often have to because you just don't have the opportunity to audition exactly the models you are interested in due to where you live. The Westone 3 is one such case where I had to rely on internet reviews, and I regret the purchase. The problem with trusting online opinions is that often the people who write really good prose don't necessarily have good taste in audio--many of them use flowery prose to describe what is essentially a severely flawed sonic signature. This is not a subjective statement--it is totally objective, because I'm judging from the perspective of pro audio neutrality, where intentional coloring of the sound is considered a sin when it comes to audio reproduction devices. In pro audio, audio reproduction has to be as transparent as possible, and the Westone 3 is anything but transparent.
In general, the W3's bass is very bloated and muddy, completely overwhelming the entire sonic spectrum. This is one of the tragedies of consumer audio, where uninformed masses with very skewed preference for heavily colored audio reproduction have managed to influence the companies who design and manufacture audio reproduction devices. These companies all should know better--they are professionals after all, but due to market demands, they are creating these very skewed devices to satisfy the uncouth public, and this perpetuates the tragic cycle. The fact that the W3 was praised to the heavens and so many actually believe its bass is perfect, is a symptom of how skewed the general public's understanding of audio is. In comparison, the bass of the SE535 is much more neutral (though it could use a tiny bit more sub-bass presence), although the SE535 has its own problems (the upper mids in the 7KHz range is way too bright/fatiguing).
The rest of the frequency range is not bad on the W3, but it also exhibits the common problem of being a bit too bright/fatiguing in the 7KHz range--this is the problem with IEM in general, since the drivers are so close to the eardrum and the shape of the ear canal causes a resonance in the 7KHz range. I suppose IEM designers can try and design around that resonance peak to begin with, but the fact that most don't probably means doing so will cause other issues.
The treble of the W3 is articulate but not nearly airy enough. This is a problem I have found with many IEM's, so the W3 is not alone in this.
The mids are fine--I don't have any complaints. It's perhaps the strength of the W3, but since its bass is so bloated/muddy, it overwhelms the mids anyway.
I have created an EQ setting that corrects the major issues of the W3, and if you are a W3 owner, I highly recommend you try this setting:
In terms of comfort and visuals, the W3 is one of the best IEMs. It's fits flush against the ear and you can sleep on your side with them on without any problems. The cable is soft and easy to deal with. The design is slick and simple. If only it sounded as good. While the Westone described the W3 as intended to be more fun than neutral, they were still very subtle with their description, and the actual sonic signature of the W3 goes beyond fun and into the muddy territory.