I have been using the Elixir Polyweb strings for about four years now. At first I was very skeptical with this concept and I thought I would rather change my strings a bit more often than to have less of a good sound.
But then I bought a Taylor and got converted (all Talyor guitars are equipped with Elixir strings). It is true that these strings are not quite as bright as brand new d'Addario strings (or others). The problem is just that the brightness doesn't stay for long. The Elixir strings on the other hand retain their sound wonderfully over many hours of playing. The Nanoweb series does sound a little better but I still prefer the Polyweb as it makes the strings feel a bit slicker. It also helps to minimze string noises during recording.
I use it on my Godin MultiAc Duet and they can really take a beating.
I don't like that after a while you get little flakes hanging from your strings. This does not impact the sound but still looks a little cheap. Another problem is that most stores don't carry single Elixir strings. So if one ever breaks you're usually stuck with buying the whole pack...and cheap they are not.
I also like DR strings but they are a hassle to get in Switzerland.