One thing that I personally would find useful is a F# like Unit of Measure, kind of type metadata, that allows units of quantities to be explicitly mentioned, a

One thing that I personally would find useful is a F# like Unit of Measure, kind of type metadata, that allows units of quantities to be explicitly mentioned, and there by help in preventing unit confusions in code, ie passing around values in the wrong kind of units, esp degrees and radians for eg, can often be a difficult mistake to catch.