Spreadsheets would be nicer if they had a coherent dataflow model. Some spreadsheet programs do this automatically, but it could be a great place for a visual programming language too.
One ugly pattern that I'm often doing is to set a column with values by the function "A3=A2" and dragging that down. This gives a column of constant values which are tweakable by tweaking just the first element. That's what a scalar variable looks like in a spreadsheet. I'd like a separate calculation area where I could refer to these. Also when I select a column I might right-click and choose "Reduce → Mean", and the mean of that column could appear in the scalar area too. With some visual tinkering you might even have a sort of "iframe" containing the columns and the scalars at the bottom of the page, and have the mean appear underneath the column to remind me what it's the mean of -- but it should float; I shouldn't have to move it when I want to drag-down the calculation to enter in a few more rows.
With spreadsheet logic you have a couple of atomic operations like, "this is a fixed column specified by me," or "this is a column containing every half-int from 12.5 through 28.5" and so on. You have reductions of those list types, like Mean and Sum and Length. You have transformations of the data too, like NormalDist(x, mean, stdev). And some of them are cached-recursive, e.g. the running-sum function you might use to find a balance given a transaction history:
balance[-1] = 0
balance[i] = change[i] + balance[i - 1]
Finally you've got a wide variety of visualizations of that data, which might also be linked from the "scalar area" -- in fact it might be nice to develop ultrasmall "thumbnail versions" that update dynamically as the data updates.
I think those elements are sort of the "core" of a spreadsheet and are handled woefully inadequately by Excel, which was not originally designed for the popular usage case it has become.