This is really the best A string -- has both power and beauty, and an unmatched range of sound color. Of course it's a gut-based string, and you have to be (or learn to be) adept at playing gut strings, with their longer play-in time and their susceptibility to fluctuations with humidity.
But the results are definitely worth the effort! When you hear all the great artists of the past, part of the amazing sound they got was from the gut-based strings, and that can not be reproduced by even the best synthetics.