When I select an HDF image in ArcGIS 10, I see 158 arrays 2 or 3 dimensions.  Both 3N and 3B are there.  When I select them, they are designated e.g.
AST_L1A_00309122010080656_20110309180648_6409.hdf:25  (4100x4200 pixels) and
AST_L1A_00309122010080656_20110309180648_6409.hdf:34  (5000x5400 pixels)
The band numbers can be seen under image properties.
Both of these raw L1A images show stripiness in the direction of satellite travel.  ArcGIS registers the nadir image fairly well (by the corners, I believe) but the 3B image is displayed a little out of register with the others, as one might expect.  There are 11*13 arrays that may have something to do with registering images, but I don't know if ArcGIS uses them.

The 3N and 3B images from silcast are in good register with each other and the underlying map.
They are both 5028x4740 pixels.  The lack of stripes and a check of pixel values show that we have a combination of orthocorrection and 1B processing.

The 3N image made with the L1B button of silcast (4980x4200 pixels) is displayed badly skewed, suggesting a flaw with the control points or their interpretation.  It seems to pad the image with extra columns, with no resampling.

The 09XT images are 4980x4200 pixels within the hdf files.  They seem well (by corners?) registered.

All bands are 0-255.  They can be seen even better with a histogram stretch.