...I just did an export speedtest.
It normally takes a couple of hours, sometimes longer to upload 200 images via the "photoshelter" plugin to my photoshelter archives. How it works is Lightroom creates a physical JPEG into a temporary folder, the uploader uploads it, then the JPEG gets deleted. It was always the export part of the process that slowed things up: the upload wouldn't take long at all.
On my first speedtest I clicked upload, went to do a couple of things, then came back about a minute later and half the images had uploaded!
So I used the stop-watch on the second test: 2 minutes 52 seconds to upload 182 images (5600 on the long side.) That's an incredible speed boost...and my computer isn't even that powerful. It will speed up my workflow considerably.