Re: There is no reason not to choose Postgres
Lotus Improv was a brilliant re-invention of the spreadsheet. I bought it and absolutely loved it. Unfortunately, it was too different to previous spreadsheet products that people had become used to. Not enough people were willing to learn a new tool, even if it was vastly superior. Poor sales led to it being killed off.
I have been messing with spreadsheets since VisiCalc on the TRS 80 and have used various versions of most of the major spreadsheet products since. None could touch Improv once you got your head round the way it did things.
I keep meaning to have a look at Quantrix Modeler to see how it compares.