1. No, deferred calculation is not supported, nor is directly setting a summary task's percentage of completion. If you would like a property that allows you to switch off automatically applying a sub-task's percentage of completion to its parent tasks, you should log a feature request; this would seem to be a very simple thing for us to add - we would just not automatically calculate a summary task's PercentComplete, and lift the restriction that prevents it from being set directly.

2. Some background: the control provides access to the timeline headers via the UltraGanttView.TimelineSettings.PrimaryInterval and UltraGanttView.TimelineSettings.AdditionalIntervals properties. This functionality was "inherited" from the UltraTimelineView control; the PrimaryInterval describes the bottom-most row of headers, and the AdditionalIntervals collection describes all the ones above it. I believe MS Project imposes a limit on the number of timescales that can be displayed; we don't impose any limit, so you can add members to the AdditionalIntervals collection to get more interval groupings to appear above the primary one. Between the PrimaryInterval and AdditionalIntervals properties, and the properties of the DateTimeInterval class (which encapsulates the timeline interval's functionality), you can get pretty much any combination of timeline divisions you like, and you can also control the width of the primary headers by setting the UltraGanttView.TimelineSettings.ColumnWidth property. That's the good news; the bad news is, we didn;t have time to provide a way to do this through the UI, so at this time, to get that functionality you would have to code it. If I get time in the near future I will try to post a code sample that demonstrates how to do this.

3. I see that we never exposed a property for this; I would consider that a bug, so you might want to submit an incident for this. Those strings are localized, so in the meantime you can use that same mechanism to change the text, like so:

TaskField taskField = TaskField.Name;
string resourceName = string.Format("TaskProxy_PropertyDisplayName_Task.{0}", taskField );
Infragistics.Win.UltraWinGanttView.Resources.Customizer.SetCustomizedString(
    resourceName,
    "This was changed" );

One thing to note is that you must do this prior to the task grid's initialization, so I would stick that code in (for example) the form's constructor, before the call to InitializeComponent. It is a static string resource, so the fact that the control hasn't been created yet doesn't matter.