Turns out iDisk is WebDAV compliant, and using a generic client seems to be far quicker and more reliable in operation than either managing iDisk content with the MobileMe BUI, or using iDisk+Finder in Mac OS – the latter of which appears to have dire performance issues.
Follow the steps (on an OSOL snv_133 x64 system)…
Use secure WebDAV (standard HTTP works okay too), and enter your iDisk address in the form of idisk.me.com/username
When dragging and dropping files to upload using Nautilus, I noticed that the “File Operations” status bar doesn’t accurately reflect data transfer progress – more often than not the progress bar will sit at some arbitrary reading without any movement. However, looking at Gnome System Monitor -> Network History one can see that data is indeed being uploaded when this happens.