I've been using ledger for my personal finances for quite some time.
I love that it has a plain-text input syntax, (so I manage all of my
ledger data files with git, and use the One True Editor as the primary
interface for data input).
The simple command-line interface has always proved sufficient to me
for quickly looping over the data file and generating whatever balance
or register reports I've needed.
That said, I don't have any visibility into what the detailed needs of
small businesses are which our esteemed editor can't seem to find in
the various "basic accounting" packages. Two things mentioned in the
article are to "generate tax forms" and "interface with an
accountant". I don't know that ledger has much in the way of specific
support for either task.
So I would guess that ledger in its current form might fall short like
many other software programs. But the fact that ledger has a real
"Unix way" about it, (focusing on the small task of defining a
human-readable data syntax, and generating reports from it), might
just make a great basis on which to build more sophisticated
data-entry and reporting interfaces.
Presumably SFLC, (unlike me), actually deals with interfacing their
ledger data with professional accountants. So those folks might have
some useful insight.