An improved UI with more customizable features would be nice (I.E. more keyboard and layout options). It would also be nice if more graphing functionality was added. Overall a handy calculator :)
Improved execution of programs. (screen updates, keyboard remains active).
New built-in "sample" programs (examples) ready to use and customize (edit).
New functions: prime and random numbers.
You can save the user's guide as an external file in your device memory.