My application requires double-sided arrows that refer to reciprocal flows, so "coming" is different that "going", but all arrrows, whether single- and double-sided (one or two heads) evidently permit only one label.
The diagram of a computer network is probably what you could most readily recognize as a legitimate need for the feature, so will use that example demand rather than my own.
When rendering an architecture of computers interconnected with other computing devices, each one has a dedicated IP address. What one packet sees "going" is different than what another sees "coming".
Anyone using the double-sided arrow might require two labels ideally on the same edge.
As a workaround I have been superimposing edges, but that generates its own breed of problems, like labels crossed by lines (a problem that will probably persist until release of the "layers" feature requested around Feb/2012) and the effort required to exactly superimpose multi-bend edges.
Most of the top 15 requested features I read about were ones that I had already felt a need for, but am a beginner (started usong yEd last week) and am just now entering this forum.
Anyway, I REALLY liked yEd. Great tool!!! Congratullations!