Did you try building your Viewer with plain labelproviders?
JFace-Databinding leads to a huge amout of listners, but that would be
explain your extrem load time > 3 minutes.

Another problem could be that your not calculating your child-items lazy
and so all of them are loaded from your backing store and not defer it
until the node is really expanded.

In my opinion the problem really comes down to the fact that JavaBeans
itself is not scalable. Requiring a listener to be added to every bean
seems an odd decision to me. When I created the framework for a model
layer about 9 years ago (pre-databinding days) I instinctively (i.e.
without much thought) created a single listener for all changes in the
model.

Databinding is not dependent on JavaBeans, that being just one pattern
for which an implementation is provided. So it should be possible to
use databinding with a model that has a different listener architecture.
However the problem is that the API for databinding is very much
centered around the idea of adding a separate listener to each element,
so we do need to re-jiggle the internal databinding code to support this.

So the current code, copied from Tom's blog:

column.setLabelProvider(new ObservableMapCellLabelProvider(

BeanProperties.value("firstname").observeDetail(cp.getKnownElements())
)
);

might then become:

column.setLabelProvider(new ObservableMapCellLabelProvider(
valueProperty.observeDetail(cp.getKnownElements(), elementContainer)
)
);

This is much the same but there is an elementContainer which would
implement a method called something like
addPropertyChangeListener(valueProperty, listener) which fires when the
property value changes in any object. Alternatively perhaps the
implementation of valueProperty should keep the reference to
elementContainer. That way the API is much the same though changes
would be needed internally to databinding.

I didn't mean 'one listener per element that covers all properties', I
meant 'one listener per property that covers all elements'.

I have published an example of how you can use ViewerSupport.bind to
bind your labels in a scalable manner. The example creates one listener
per property (table column) regardless of how many elements there are.
I have documented this at nwestbury.wordpress.com.