My experience has been Nanowebs help a little (I haven't used Polywebs in years), but then you're getting into timbral differences as well, and not nearly just string noise as an artifact. I like Elixirs for the convenience; it's great to pull my Martin out of its case and have it still sound pretty fresh, without having to change strings every couple weeks just to get decent tone out of a guitar that only gets played a few times every couple weeks, but even I'll probably switch to something else once I stop demoing and start recording in earnest.
And anyway, they help a little. They don't make it go away, just seem to lessen it a touch.
A lot of it is technique, like anything else you need to practice not brushing your fingers across the strings when you switch chords. However, and in the interest of full disclosure I'm a bit of a sonic anarchist, and get off on stuff like Tom Waits and Porcupine Tree where noise can be just as much a musical element as any actual melodic line, but I LIKE string noise. I like those little elements and relics of humanity that creep through a performance and remind you that you're listening to a guy with a guitar, some strings, and his own two hands. There's a fine line between having it become annoying (poor technique) and having it lead to a more human performance, but as long as it's not too over the top I'm pretty cool with it.
