The AI-S 55/2.8 micro was central to my lightweight travel/hiking kit many years ago. In combination with a 20/3.5 or 28/2.8 and a 135/2.8 I had the flexibility of a wide-angle, standard, telephoto and macro, all with a reasonably fast aperture.
The 55/2.8 micro is not perfect as Airy points out. It's a little over-corrected for spherical aberrations which is why the background rendition is nervous (it improves at close range) and the foregrounds are smoother. And it does not like shooting into the light, even late copies with SIC coatings, but I rarely found this to be a problem as the front lens is well shaded. Working distance is also short for true macro work but it's useful for casual closeups in the range 1:6 - 1:3 that normal 50mm lenses can't achieve. Otherwise it is a very well balanced lens - sharp with good colours and contrast, fast enough for most purposes, well-built, compact and affordable.