Starting in ArcGIS 10, all raster format support has been improved. You should not see a change in how your data is handled; it should work as it always has.
The main purpose of the improved format support is to overcome many of the limitations of the old format library.
The improved format support enables ArcGIS to read and write out more raster formats. As well, there are more TIFF compressions available when creating a TIFF file.
All new pyramids created are now saved as an OVR file (with the exception of the ERDAS IMAGINE® format). The new OVR files are more flexible since they work with all file formats that allow for pyramids. As well, the OVR files can be compressed so that they do not take up as much disk space.
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