I like both the Signature and Classic PRS strings, I recently tried both against each other, and my previous preferred sets (DR Pure Blues and Tite Fits, depending on the guitar), and they compared well.
The Signature strings, to me, are like EMG pickups or Floyd loaded guitars, in that people say the guitar starts to sound more like the pickups, or like a Floyd, than anything else. I’m not a big fan of either of those items, but in the case of these strings, it’s a good thing, even though they start to dictate the tone more, they sound very good. The wound strings are punchy and articulate, the plain strings are very slightly warmer sounding than average, just to avoid being harsh. I think it aligns with what Paul said players were looking for and finding in the 594, very articulate down low but smooth and not harsh on high notes.
I’ve tried them on a few guitars and they sound great every time. That being said, I’ve only got 2, maybe 3 that I’ll continue to use them on, because some of my other guitars, I want to let other characteristics of the instrument shine through, and I don’t want all my guitars to sound the same. They feel essentially the same as the Classics and my former DR’s.
Oh, and yes, mine have also lasted a long time and kept their tone and brightness, like
@dogrocketp mentioned!