If you do a "total" line, please allow the end user to define an aggregation function. Total is not flexible enough to cover many use cases.

The google tables also display "formatters", which are a nice way of formatting the underlying data. For example, the BarFormatter automatically adds a horizontal bar next to each number, the widht of the bar proportional to the value. That is a very nice visual. If you could do something similar to their formatters, that would be excellent.