I've uploaded version 1.4 beta 1 of pyparsing to SourceForge, it represents some significant reimplementation of some of the core parsing classes. The major change is the conversion to use internally generated regular expressions, plus the addition of the Regex class for user-defined re's. My performance tests show a 30-40% improvement in parsing speed.
For those looking for additional performance enhancements, the oneOf helper method has been especially enhanced to generate a regular expression, instead of the previous list of Literals within a MatchFirst class. oneOf is especially useful for taking advantage of performance gains, since it is compatible with version 1.3.x programs. The Word class has also undergone similar enhancement, as have several built-ins for comments and quoted strings.
All of my regression/unit tests have passed, but these changes may have some unexpected side effects. I'm also interested in any feedback on the current implementation of Regex.
Please post beta test feedback to the SourceForge developer forum.