FWIW Ive rarely had a problem breaking out of ping/traceroute/etc on a Cisco.
I have found that Shift-Ctrl, then a very very small delay and 6 (while
still holding down Shift-Ctrl) works like a charm every time.
Maybe the terminals I use are just more friendly towards that sort of key
sequence than others. 
Though the only thing it doesnt seem to help with is when you have no DNS
servers configured and mistype "configt", or some other command that
doesnt exist and it tries to resolve it through broadcast several times.
Ive found its futile to try and get out of that.
Tom