Pros: Alessandro-like tonal balance; great detail for the price; great soundstage ambience for a supra-aural design.
Cons: Low bass lacking; mid-bass hump; bass is a bit muddy; highs mildly sibilant; detail isn't on the same level as better headphones.
What can I say that hasn't been said before about these?
For $15 you can hardly go wrong! The tonal balance is similar to my Alessandro MS-1is, although with noticeably poorer bass extension. The bass is also noticeably a bit muddy comparatively, but seems to improve a little with amplification. Bass impact depends on how tight you have them on your ears - right now, with them a tiny bit looser than stock, both the MS-1i and my HD 600 have more bass impact. That has surprised me a bit, especially after hearing the PortaPros and having been overwhelmed by relatively muddy mid-bass.
The detail isn't quite there at the same level as the MS-1i or any other 'phones on that level or higher, but again it's remarkable for the price. Both midrange and treble have a similar level of detail - good but not great, and definitely not excellent on an absolute scale.
The soundstaging of the KSC75 is a bit of a surprise - so far I've noticed two things: The ambience and sense that the sound is coming from farther away from your ears than a few fractions of an inch is excellent. On the other hand, the imaging (i.e. preciseness of direction in which sounds appear to come from) is rather poor.
As for looks - well, they're rather hideous. Like wearing a pair of clip-on aftermarket hubcaps of the cheapest kind on your ears. This is only the second worst part of these headphones though...
The worst part of them for me, so far anyway, is the comfort. "Ear rape" is an appropriate term. I've been playing around with the clips, and unfortunately, it seems that when I loosen them up enough to be moderately comfortable, the drivers are too far away from my ears. Tighten them back up to about stock for proper distancing of the drivers, and they pinch my pinnae painfully.
I don't know, maybe I'll get used to them or find a more comfortable configuration of the band. I do admit that the headband-less design is intriguing in terms of portability. I'm not a big fan of IEMs in terms of comfort or soundstaging, so that's not really an option for me.
One interesting possibility is that these may be decent headphones to sleep with - my preliminary wear testing seems to indicate that they aren't any less comfortable when resting the side of your head on a pillow.
UPDATE (January 8, 2012): I've certainly come to like these a little bit more over time. I don't use them very often, but I did get the clip clamping dialed in/got used to them. They're reasonably comfortable now, but my ears are still a little sore after an hour or two. It's a marked improvement and for the price not bad.
With more listening, I also found the sound to be rather sssssibilant. -3 dB at 9000 Hz (0.7 Q) on the equalizer fixed that, and now the treble sounds much more refined. I've also thrown in a little bit of bass and lower midrange boost to suit taste, but the important thing was taming the sibilance.
Now I probably wouldn't hesitate to have these as my only headphones for a short ultralightweight trip - I think I prefer them to my Shure E2c's. Those were my gateway drug, too.