ZPE 1.9.7 (Galashiels) is one of the most solid updates yet. Many major bug fixes have been introduced, new performance gains and a new typing system (TYPO v2).
TYPO v2 is perhaps the biggest improvement to the whole ZPE Programming Environment in the last few months, and it changes the whole way that it works underneath. Instead of doing type checking at compile time and thus making starting and interpreting programs/scripts slower, it is now done at runtime. The impact here is actually slightly smaller and relies on the underlying implementation of variables to perform this check.
TYPO v2 also removes the STRONG_TYPED property from the properties list and allows side by side strongly typed, statically typed and weakly, dynamically typed variables to be declared side by side in a single program or script.
All ZPE/YASS documentation has been updated to reflect this new change, particularly the page on Assignment and variables.
ZPE 1.9.8 is looking to use more static hidden objects to improve both performance and lower memory usage. This might be another big update.