1. Increasingly, new computers are shipping without Java installed, whereas they all seem to have the Flash player pre-loaded.
2. As Java has grown, it was taking a very long time for applets to load. On slower computers, it can take up to half a minute to load a Java applet after a reboot. Flash applets take about a second.
3. The internal architecture needed to change anyway to allow for a future graphing version.

Over time I plan to rewrite all the applets in Flash for the same reasons. The rewrite also gave me a chance to add some extras:

• There are some new functions: ln(), abs(), ceil(), floor(), round(), max(), min(), pow(). Some of these are paving the way for a graphing version. See Calculator instructions for details.
• The display now scrolls so you can go back and see earlier results.
• A "Print" button that prints the calculations, including those that have scrolled off the display.
• An "undo" button to delete recent work. The value of "ans" is restored to the last result before the deleted calculations.
• The "number of places" control works differently. It now controls the number of significant digits after the point. For example, before, if the result was 1.002782, and you displayed 3 digits you got 3 digits after the point, or 1.003. Now, you get 3 digits after the last zero after the point, or 1.00278. This means that results that are close to but not equal to zero do not look like exactly zero, even if you are asking for a few decimal places.
  
  This solves an issue that confused many users, for example if you display 3 digits you could get a result like: 2 + .0001 = 2 , which while correct, looked like a calculator bug to many. You will get 2.0001 now, even if the calculator is set to 2 places.
• A button has been added for the exponentiation operator (^). 2^3 = 8. (Two to the power 3). Entered on the keyboard as 2^3 or pow(2,3).
• The "Full size" button is now on the calculator body. Press ESC or the "Full size" button again to return.