« Good, but not great.  »

I recently had my guitar professionally set up and asked for the new (ish) Ernie Ball Cobalt strings. I have been playing the standard Ernie Ball regular slinky strings for over 10 years. I have typically played .10s, however I had a specific project that I have been working on where I was tuning my guitar to standard D instead of standard E. Therefore, I wanted to step up to .11s instead of .10s. I have about twenty sets of the Ernie Ball .10s at home, so I wasn't interested in trying out the Cobalt strings until I used up all these strings first. However, because of this new project, I decided I would try them out for the time being.
My initial impression was that they sound the same as a fresh set of the standard Ernie Ball strings. I didn't hear that the 'Cobalt' and extra $$$ was making any different. This was a little disappointing because I would have hoped that the strings would sound better in general when you first put them on fresh. The second test was whether they hold their tone for longer. I have been playing them for about a week, and it is hard to tell if they have really been able to hold their tone longer.
The one thing that I do notice, is that they are easier to clean than the standard Ernie Ball strings. Any dirt or grime from my fingers that gets left on the strings comes off pretty easily. This definitely helps the tone last longer in the strings, because it helps the strings vibrate more smoothly. I try to clean my strings after every time I play. Anyone that plays guitar knows, after a while, it doesn't matter how much you try to clean your strings, the dirts not coming off and it is just easier to put a new set on. I am hoping that these strings last a little bit longer to make the extra $$$ worth it. Otherwise I will probably just stick with the cheaper strings.