one mistake (like letting up on the control key slightly while clicking, or trying to use the arrows to scroll the screen) blew away all the selections he had made.

Something to understand about RMM... You don't have to do everything all in one go. You can start synching just one album, and then continue on down the list without interruption. The synching happens in the background so there's no need to do the big Ctrl-Click on the list trick.

Interestingly, it handles deletions smartly, too. For example, if it's still synching and hasn't gotten to a certain album yet, and you select the Karma and then select that album on the Karma and say "Delete", it'll show up in the detail list as "Cancelled" and it just won't bother to transfer that file. If you run out of space on the Karma and the synch stalls, you can select the Karma and begin deleting albums, and it'll delete them and then pick up the synch where it left off.

I understand your issue with having more music than will fit on the Karma. So I handle it a bit differently. I select the entire music folder and synch it to the Karma, so the percentage bar at the bottom indicates "red" at the end. Then, as it's still in the middle of synching the music, I select the Karma and start fishing through and deleting stuff I don't care so much about until the bar isn't red any more. I don't think this was their intended way for me to do this, but it works.

Another option is to use the synch profile feature that has it replacing the contents of the player based on stuff you've listened to recently. It'll delete stuff off the player that you've recently listened to, and replace it with stuff from your PC that you haven't heard in a while.