(another from Mike)
hey all,
I would think that for format=app/openlayers, it would be more appropriate to use the OpenLayers.Layer.WMS.Untiled class. Since this format= will first and foremost be used for people to sample their WMS' in GeoServer, I would think you would want to make more 'pure' WMS requests which aren't subject to any of the sometimes-weird behaviors of Tiled layers.
thanks,
mike
--
Chris Holmes
The Open Planning Project
http://topp.openplans.org