Michael,
We are using the same third part dll for EcwRasterLayer and MrSidRasterLayer. There is a knonw issue that we didn't take a good advantage of the built-in caching for MrSid, and I think maybe we have the same issue for EcwRasterLayer. We haven't solved this problem andI think there should have some performance improvements after we figure it out. Maybe in the next version, we will have a faster MrSid/Ecw Raster Layer.
Here is the link about MrSid's performance issue, please have a look if you are interested.
gis.thinkgeo.com/Support/Dis...fault.aspx
Thanks,
Bai