Soundwise they are full and harmonically rich with a mellow treble, lending to clear melodies, singing harmonics and full sounding chords. Overall a very warm sound.
The flatwounds feel very smooth compared to the roundwound bottom string. Bends feel smooth. Very nice feeling strings.
The only thing that keeps them from being perfect is their quality. I have broken a couple of strings at the tuning peg because the windings do not reach all the way to it. They do last for a very long time, as long as you keep them clean. They are comparable to elixirs and d'addarios (NYXL, on my electrics).
TL:DR; Excellent strings, especially if you do not like the harsh treble of steel strings.