The hierarchy feature enables the ability to quickly change the level of detail in a Gantt view, by collapsing and expanding subtasks. It is very useful for conveying the action plan for a project.
A Gantt chart grouped by resource is a convenient way to do simple resource management. Once can easily see which resource is assigned to which task.
However, grouping appears to only operate on the top row in a hierarchy. Is this correct? So, these two features clash when one tries to do resource management. A hierarchy of tasks wherein subtasks are assigned to different resources (contributors, equipment, workstations, etc) cannot be separated into different groups.
I think there would be a lot of interest in additional features to support resource management on Spreadsheet.com.
I suggest three features that I think could enable more resource management capability while also being lightweight and flexible.
Grouping options to allow rows to be members of multiple groups and descendent rows in the same hierarchy to be members of separate groups. It would be wonderful if the groups could be defined just like filters. The filter feature keeps ancestors if a descendent is selected and that retains the collapse - expand functionality. I think it would be very valuable if the same could work for groups, but that would require ancestors be members of multiple groups.
Ability to add an additional label to a gantt bar. For example, the cost of a task or the fractional load of a worker.
Ability to add a roll-up display over a Gantt chart, for each group. The image below illustrates the concept. Suppose that a user-defined roll-up function were evaluated for all tasks that intersect each calendar segment. The calendar segment adjusts as one zooms in and out. So too could the date ranges for each roll-up segment. Moreover, conditional formatting could be useful to highlight certain cases, like over-allocation. If such a roll-up display were created for each group one could easily see loading across a group and quickly identify any tasks that need review.
I look forward to the further development of Spreadsheet.com. It is a very nice tool.