It’s no longer dependent on SoftwareSerial (though it can still be used if desired). This brings compatibility with more and newer boards such as the Arduino Due that have multiple hardware serial interfaces but no SoftwareSerial support.
Adjustments have been made for the most recent printer firmware, so features like inverse printing and barcodes have returned.
Extended character support. The latest printers provide quite a few international character sets and symbols in the upper ASCII range (characters 0x80-0xFF).
Existing sketches will need just a few lines updated, it’s not quite a drop-in replacement. See the examples included with the library for an explanation. This was necessary for adding hardware serial support.