Lots of changes in the latest update:
Support for OS X Yosemite, including a Notification Center widget for quick calculations simply click on the display to switch to the main app, even mid-calculation.
Handoff support, between PCalc running on iOS 8 and Yosemite – continue your calculation on any device. The full state of the calculator, including the tape, is sent over.
Support for custom button layouts created with the iOS version. Full editing on the Mac will come in the next release.
Visual improvements, to match the new look of Yosemite, and unify with the iOS release.
A new dark calculator theme, “Backlight”.
All the core calculation code improvements from PCalc 3.3.2 on iOS, including better operator precedence support.