Or you could do what I do: make a local copy of your iDisk. (It's an option on the MobileMe sync preference pane.) On my MacBook Pro, I use a local copy with manual syncing, and on my Mac mini, I use a local copy with automatic syncing. That way, my Mac mini server is always updated with what's on my MBP, and access to iDisk files is very quick regardless of which system I'm using.

I think the upside of using the Transmit method over having your iDisk make a local copy is the ability to have those files also backed up through Time Machine. Currently Time Machine will back up the sparseimage that contains your local copy of your iDisk, but its a bit of a pain to revert to an old version of one of those files. With this method, the local copies are just a folder like any other and get backed up normally.