Warmth -- literally warmer to the touch, washi feels soft and creates a feeling of warmth in the viewer. Its tactile qualities make it wonderful for invitations and books. 
Body -- since the fibres are left long and pounded and stretched rather than chopped, washi has a deceptive strength. Pure-fibred washi can even be sewn and was used for armour and kimono-lining in earlier times. 
Strength -- the length of the fibres and the nature of the raw materials ensure that washi is highly workable when wet. Thus it is excellent for papier mache, and etching in which the paper must be soaked. These long fibres produce a luxurious deckle edge, the rough edge which marks a handmade paper. 
Soft translucency -- kozo and mitsumata are naturally translucent fibres, a quality specific to paper from the East. As such, it is used regularly for the transmission of light. 
Absorbency -- the nature of the fibres creates a ready absorption of inks and dyes. Papers that are "pure fibred" and dyed will result in much denser and more vibrant colour when fabric or watercolour dyes are applied. 
Flexibility -- since the fibres position themselves at random, there is no real grain to washi. This gives the paper a resistance to creasing, wrinkling and tearing - and means it can be used more like cloth, for covering books, or boxes etc. 
Lightness -- washi weighs much less than other papers of equal thickness. As a paper for books, it can create texts of apparent weightlessness. 
Low acidity -- traditionally-made Japanese papers are truly acid-free if they are unbleached and unsized. Examples of printed papers exist in perfect condition in Japan from 1000 years ago. Today, papers from the village of Kurotani are among the finest archival papers. 
Decoration -- for centuries, colourful designs applied by woodblock or handcut stencils have created vividly characteristic papers, for decorative use. Recently, silkscreened chiyogami (small repeated-patterned paper) is available in an unbelievable range and widely used by craftspeople. Although made by machine, the quality available is about 70% kozo and comes in hundreds of patterns.