EGanz, does hugin export metadata for how the JPG should be projected?
ICE and the Photoshop plugin both convert your panorama to a perspective-corrected cube map and converts each side of the cube to a tiled multi-resolution tile pyramid.
As of right now, this is all done client-side. Perhaps that will change once Read/Write World is up and running and has its tiling services available.
As of right now, the Photoshop plugin that Matt linked to is your best bet for uploading your high-res pano from hugin. Uploading fine tuned, edited, or stitched-with-other-stitchers panoramas is exactly what the Photoshop plugin was created for.
There is no effect without a cause.