These have excellent mids, vocals sound very sweet, typical Shure.
Good treble with some sparkle, although less sparkle/piercing than the normal SE535, but more refined.
Bass is great, low and punchy, not overly emphasized, just the way it is meant to be heard.
Soundstage is okay, not as big as the Westone 4.
 
Sound isloation is excellent, for me it's better than Shure SE315 and SE215.
Very comfortable and snug with the black foam tips.
Cable is robust, but I wish it is longer by like 10cm, right now it's 116cm.
 
Although they say "enhanced high frequency response", the red 535 aren't that much better than the normal 535, just a little less emphasis on mids and a bit more details in the treble, same bass reponse.
 
The red SE535 are much more passionate and engaging than the Westone 4/4R, which are probably their biggest competitor, I prefer the Shures over the Westones; just my opinion. I highly recommend these earphones.
 
 
UPDATE:
I've had them for over a month and I'm very pleased with what I'm hearing. They don't seem to change that much with burn in.
I've also realized the black foam gives a better sound than the gray silicone tips, the foam has more bass, and has a fuller, richer sound, while the gray silicone has a cold, metallic sound with harsh treble, and less bass. It's a very minor difference by the way.
The nozzles of the red 535s seem quite delicate, I could heard squeaky sounds from them when I was changing the ear tips.
 
 
 
 
 

I got my Shure SE315 as a gift, and I absolutely love them, here's the review:
 
Build Quality:
 
I think the SE315 has excellent build quality, with its detachable and robust cables, L shaped jack, they have no issues in daily usage. I'm not sure about using them on stage since I don't, I only use them for personal listening on my computer and iPod.
 
Comfort and Isolation:
 
The sound isolation of SE315 is AMAZING, the best in all of the earphones I've ever tried. Black foam sleeves that come with these earphones provide the best isolation for me, people talking right next to me is almost inaudible even without music playing. At first, the shape of the SE315 looked really weird to me, but surprisingly, they fit tightly and snugly in my ears, and the over the ear design keeps it in place during physical activities.
 
Sound Quality:
 
Highs:
 
The highs of SE315 is nice and controlled, not too fatiguing. The highs are much better than the SE215, in both quality and quantity, it extends higher and is more forward. But I would like it if it can go even higher, because in some songs, violins or pianos can be a little faint.
 
Mids:
 
This is where these earphones are better than most of the ones I've tried. Shure earphones are known for their mids, and these sure don't disappoint. The mid is extraordinary clear and forward. Vocals sounds awesome, like you're sitting right next to the singer.
 
Lows:
 
I'd say the low end (bass) is the weakest part in the sound quality. Bass goes pretty low, but lacks some punch. That's where the SE215, with dynamic drivers, are superior to the SE315.
 
Soundstage:
 
The soundstage is larger than SE215, it feels like the music is surrounded horizontally around you, but not so much vertical depth.
 
Conclusion:
 
I enjoy the SE315 very much, although I prefer them over the SE215, the dynamic drivers of the SE215 is more fun to listen to, therefore I use both of them. I recommend the SE315 for those who wants clarity and precision in their music, bass-heads might need to look somewhere else.