There has already been a lot of testimony expressed here regarding the
merits of abc as a musical notation, provided mostly from a personal
viewpoint. Perhaps, though, a few more words could be added considering
the question from a wider perspective, considering both the intrinsic
advantages of the notation (as compared with alternatives) and the
practical, situational advantages that the use of abc offers the
contemporary user.

First, it has to be noted that the simple fact that music written in
abc is expressed as a string of standard text characters, to be found
on any keyboard, is of tremendous importance — no special environment
or device or software is needed to enter or display an abc
transcription. As has been noted, a useful bit of abc can be (and, I am
sure, often has been) scrawled on a cocktail napkin for future
reference. Transcriptions expressed in abc can be compactly stored and
cheaply transmitted, with assurance that the content can be read
unambiguously at the receiving end. Stored abc transcriptions can be
easily edited, searched and indexed with standard text-oriented
utilities. Because abc piggybacks on the text-based infrastructure of
our literate society we can be sure that the abc we write today will
still be intelligible hundreds of years from now (assuming of course
that there is still anyone around to read it).

Further qualities of abc that argue for its continued use (some of
which have already been noted in earlier posts) are:

* abc provides a natural, readable translation of traditional music
notation. The correspondence between the graphic elements used to
portray a score via "dots" and the symbols chosen in abc to correspond
to these elements is direct and intuitive. A musical bar is represented
by a character that looks like a bar; there are very few, if any,
arbitrary choices of characters to represent a musical idea in abc.
Anyone who can read standard musical notation and is comfortable with
the naming of pitches with alphabetic characters can immediately grasp
the correspondence. It is even reported to be possible, with practice,
to be able to visually apprehend a written-out abc transcription to the
point of being able to directly play off the music it represents
(though probably few individuals are likely to ever get that
practiced!).

* abc is concise. The critical information about a tune setting is
noted immediately, in just a few lines. The details of an actual line
of music can be captured with extreme economy, in mere seconds.

* abc is capable. As the idea of abc has grown and spread over the last
thirty-odd years, ever-more-refined ideas have been worked into the
basic concept, to the point where (as is attested to by the
correspondence on this list) notational challenges that it was surely
never dreamed that abc might ever need to meet have been incorporated
into the understood range of the notation. Another way of putting this
is to say that abc is extensible, capable of growing to meet
newly-perceived needs.

* This is possible only because abc is an open notation — no-one owns
abc. Any user can do whatever he or she wishes with the notation; the
only test of what modifications or additions to the understanding of
abc may occur is public acceptance.

* abc has been accepted. Unlike other music notation systems that have
never gained more than local, marginal use, there is at this point no
question about whether abc will take a permanent place in the set of
notational tools our society uses to store and carry forward our
accumulated cultural heritage. No longer just the parochial plaything
of a small community of enthusiasts, abc has become widely enough known
and used to serve as the basis for major public projects that would
never have been undertaken without its availability, and it is becoming
increasingly important for anyone involved with the distribution of
bodies of transcribed music (especially copyright-free bodies of music)
to pay attention to abc.

* abc is supported. As others posting here have noted, there is a very
wide range of excellent software utilities available to anyone wishing
to work with abc transcriptions, in almost any current operating system
environment. This has been true for a long time, of course, but the
fact that vigorous development in this respect continues and that
support for the abc user has been extended to at least one open
internet utility is highly significant. It is really inconceivable at
this point that abc will be left an "orphan", as has happened to so
many other beautiful schemes that have appeared to great fanfare, only
to fade away again, over the several decades now since the computer
revolution started shaking our society.

In short, it appears that you can at this point safely put at least a
reasonable number of your eggs into the abc basket.

/RWWT