Usually it takes a few walking cycles when tux starts walking until the footstep
sound is played.
I guess this has something to do with the two play_steps blocking each other
and/or not being reset properly, once tux comes to halt.

Or maybe we need to introduce a second running-only cycle and only use that one
for running sounds.

I do not really understand your comment.
The sound is played only when Tux is running, not when he is walking.
Your reference to the walking phase *and* the running phase are thus a bit
confusing.

Any comment, matthias ?

Ok, it seems to work fine when you hold shift key to run, but using "u" to run
(toggle running on/off) the problem occurs.
Yeah, I meant the running cycles instead of the walking cycles, sorry. :)

Is that really a release-blocker, matthias ?
In my opinion, it's at most a 'bug'.
Do you agree to lower its priority ?

Ok, let's downgrade.