I've dealt with a similar system a while back and I found it to be a real pain in the ass. Had several interactions with that particular company their support desk, and would always get a call back a couple of hours after I initiated the call. Every time I got the call back I was either in a meeting, taking a shit or driving. Never sat behind my computer with all the info available, and it quickly became an endless loop. I much rather deal with queues, because it means that my mood is still set on fixing the issue, rather than on something else.

It would be cool to have both options, call back or queue.