Ah thanks, looks like it has some interesting features. They seem to have chosen to add an 'Ans' variable in there, which I suppose also works. At least it avoids the issue where you calculate something, need its logarithm, and you just can't.

For now I'm using RealCalc, which is about the only one that I can find that has a 'normal' calculator mode (i.e. infix for binary operators, suffix for unary). Though it also has an RPN mode, which is quite useful.