As with all in-ear 'phones the sound depends on the fit in the ears, and that's really important with the SuperFi 5. To me, the SuperFi 5 is reminiscent of good open back headphones. Vocals can sound quite intimate and clearer than the SuperFi 3. On the right material, instruments are placed in a wide sound stage for example, some of the tracks in the Corrs "Talk On Corners", and the Samantha James' Rise acoustic sessions tracks have a big sound. The brighter sound that works with vocals can make high hat cymbals a bit prominent. Bass will be heard if it's in the mix, and synth bass sounds good provided that the ear pieces fit well; the bass in Lady GaGa's "Fame" and "Poker Face" can sound quite percussive. You need to sit still if the cables are not looped over the ears, as any movement is readily heard as thuds and clanks. The sound does improve from new after a few hours use.
At long last the earpieces are colour coded for left and right. Unlike earlier SuperFi models, the cable is not replaceable. Whereas the SuperFi3 came in a sturdy aluminium container, the SuperFi 5 has a plastic hardshell container.
As the cable is thinner and more flexible than earlier SuperFi earphones, I have some doubts that it will withstand the occasional "lassooing" of Spin bike handlebars in the gym. If not, then it will mean buying the complete earphones! I was really surprised that the Comply foam tips not only stayed in place during sweaty treadmill sessions, they even remained in place during extended side planks on a Power Plate! The sound isolation really works in the gym so that I can exercise in my own musical bubble.
Although my SuperFi 3 earbuds lasted almost 3 years of gym sweaty sessions, the right earpiece in the SuperFi 5 failed in two sets shortly after purchase when used in the gym. The third pair started to fail in February 2011.
The Comply foam tips are really comfortable - I've twice gone to sleep with them in position - but quite costly to replace.
When one of the earpieces failed in my well used SuperFi 3 'phones, Logitech were unable to replace the earpiece, but gave me a significant discount on a replacement (I choose the SuperFi 5). They have also been helpful (yes, I would have expected them to be) when the SuperFi 5 failed after three weeks, and the two replacement pairs also failed. They have replaced the SuperFi 5s with the successor 700s which are an improvement in sound quality
There have been quality control issues with the right ear piece and although it now lasts longer, the problem has not been solved. Ultimate Ears are now owned by Logitech and there seems (to me) to be cost cutting issues. The sound is good, but their longevity is questionable, care is needed in the gym, and Logitech no longer sell this model (replaced by the 700), so there needs to be substantial discount from the recommended retail price before they are good value for money. If you can afford it, try the 700s.