"You can't go wrong - literally"5.0 starson by LosTresGatos
Pros: excellent lows and mids, lightweight buds, unbelievable value
Cons: a bit weak on the highs (although my opinion is a bit skewed - read the summary for more details),
Summary: I got these S4s out of curiosity - originally I bought a pair of Monster Turbines, but they didn't fit my listening preferences (way too much bass) and so I did a partial exchange with the S4s after reading glowing reviews on Cnet.
For reference, I own 4 pairs of earbuds - Shure E3G & E500PTH, Ultimate Ears superfi 5 pro (*NOT* EB) & triplefi 10 pro. As you can see, my tastes run expensive and the Klipsch are by far the cheapest earbuds I own.
IMO, they're frigging amazing. Outright they beat my Shure E3s in all aspects, and I don't just mean sound - they're lighter and more comfortable to wear too. Low end outperforms both of my Ultimate Ears as well, although I do think the triplefis have a cleaner bass sound (albeit not as strong as the S4s). Mid range is amazing - close to par with the E500 and triplefi 10. The highs are the only letdown - I found both Ultimate Ears and Shure E500s to have much much brighter and crisper high notes. The Klipsch sound tinny in comparison.
Outside of sound reproduction, the Klipsch S4s also have a huge ace in the hole in that they're so compact. Both the Shures and Ultimate Ears have tons of technology, but that's because they pack em into earbuds the size of lego blocks. I have no idea how Klipsch was able to pack in such great sound reproduction into an earbud that's literally 1/2 of the length and 1/3 of the weight of a Super.fi 5 pro. They're also very light - yes, that *could* mean they're flimsy as the Cnet reviewer reported, but until they actually break, I'll give Klipsch the benefit of the doubt.
My overall conclusion: If you're looking to upgrade and have a budget of $130 or less, stop reading and get these - no way no how is there anything better period. Even my brother's Bang & Olufsen Earpiece 3 sound like crap compared to this.
If you have a bigger budget, then musical preferences come into play. Personally if I had to pick only 1 pair of earbuds, value for money it would be the Ultimate Ears Super.fi 5 pro (no EB - the extra bass screws up the sound) for around $200. If low end bass is your thing, try out Monster's new Turbines - it has unbelievable bass, but I'm not sure if it's worth the extra $50-60 over the Klipsch.
As I said though, you literally CANNOT GO WRONG with these S4s. The fact that I was comparing them to $200-$500 earbuds speaks volumes about how much quality is packed into an $80 package. And they will be used regularly by me - nobody wants to use $500 lego blocks while running outdoors or working out in the gym. Not only are these compact and lightweight, the bud design doesn't require you to loop the cord over your ear for support - they hand straight down so no sweat trickling down the cord into my ear *AND* they don't get dislodged when I wipe my face with a towel.