BUGS

Using Equations w/o titles results in incorrectly numbered
  equations with titles.  Use InformalEquation instead.

InlineEquations don't work in the RTF backend.  It's not my fault.

Callout support is somewhat fragile.

Line numbering of linespecific displays is somewhat fragile.

In two-sided mode, with the RTF backend, the appropriate
  alternation of inner/outer headers and footers does not work
  correctly unless %page-number-restart% is true.  This is
  caused by a limitation in RTF.

CHAR alignment in tables is not supported

The stylesheets can't automatically put callout marks on a
PROGRAMLISTING or SCREEN if the text comes from an external file
using the LINESPECIFIC INLINEGRAPHIC trick.

"Extra" </P> elements appear in the HTML output if you put block
elements inside of <para> elements in your source. The problem
is that

  <para>Some text <table>...</table></p>

Is translated into

  <P>Some text <table>...</table></P>

but HTML doesn't allow "table" inside a P, so the begin table
implies an "</P>" which makes the </P> after the table erroneous.
I don't have a good answer for this, but I'm tempted to make all
<P> tags empty in the HTML so that the browser has to imply all
the </P>s.