rutherford
Master Black Belt
Short answer: Yes, it's very important. I've mostly seen it done as part of every training experience so that there's always some component of foot trapping in play and perhaps the instructor will comment on it and perhaps not. I have seen few drills which isolate foot trapping, like you would find in Silat's lower art drills.
A recent thread on this topic: http://www.martialtalk.com/forum/showthread.php?t=24332
A recent thread on this topic: http://www.martialtalk.com/forum/showthread.php?t=24332