I bought these strings because of the exposed core so that I could lower the action artificially on a guitar that I own. That works great but also I have been very impressed by the quality and longevity of these strings.
The sound is quite bright but still with quite a bit of body on the lower strings. To me the sound of them seems quite well balanced between highs and lows. Great for electro acoustics.
They seem to have lasted me quite a while too. I put them on my guitar to do a gig and have just kept them on for a while after and they are still plenty bright and sparkly.
I was informed of Rotosound strings by a rather reliable and trustworthy source. They are lovely strings which retain their bright sound for some time. The wound strings are stripped bare at the ends so that the thing core of the string touches the bridge which provides a rather lovely sound on Semi-Acoustics with pickups in the bridge. My problem with Rotosound strings however are that for my playing (I can really get into playing songs), the strings can break easily. Which isn't ideal. However for those who play mainly soft finger picked songs, this strings are pretty perfect.