The new Ernie Ball Cobalt flat wounds replaced the excellent Thomastik flats I've used for many years on an Ibanez semi. The obvious advantages are that you can go one gauge lighter, and bend the g string. I also found that the top end of the Ernie Balls is clearer.
Playing feel is smooth and effortless. Cobalts in general always need a day or two to settle in, in terms of playability. After that short play-in period, they play great and sound great for a long time.
Sound and response of the strings is clear, dynamic, effortless. You can easily control the sound with different playing techniques.
Highly recommended.