What's new since version 4.1?
An additional two man-years work.
8000 new "good move" patterns handcrafted by Japanese 6 dan.
Radical improvements to fuseki system.
New algorithms to improve life & death accuracy, especially living by "running to centre".
New system for changing play style when behind.
Improved play against central moyo strategies.
Improved connection strength algorithm.
Plus hundreds of tweaks and bug-fixes.