His preferred calculator seems fairly close to using ipython which is what I would do.
Also, I have to admit that python 2's default behavior regarding integer division is not what one expects from a calculator (I expect 3/2 = 1.5).
I'd rather use my existing knowledge than learn how to interface with something that is probably not as robust or as well designed.
I only recently discovered that there's a lot more to R than intuitive division of integers ;)
Just the other day my pregnant wife asked me to calculate the aprox date she'll give birth (considering she has 17 weeks) ...
from datetime import datetime, timedelta
print str( datetime.now() + timedelta(weeks=40 - 17) )http://pubpages.unh.edu/~mwidholm/MathPad/
Really served me well in college. I've heard it referred to as a "Poor Man's Mathematica" back in its day. If Soulver worked more like this, I would have bought it by now.
That said, I've found that using my iPod touch as a "real world calculator" is much more convenient, and I ended up buying PCalc for it.
http://www.pcalc.com/iphone/index.html
Being able to tap calculations while walking and pacing the room brainstorming tended to be more useful than being forced to sit down and type at a keyboard.
These days I use irb (Ruby) or ghci (Haskell) for all my calculating needs. For me, defining functions and being able to map and fold are very important.