At this point, if I were to vote for new features....

[parisse]

Indeed, if you store in a list with :=, a copy of the list is created. This is of course inefficient but it prevents side-effects like for example if you create a matrix with 1 everywhere like this
l:=seq(1,3);
m:=seq(m,3);
and if you modify in place one coefficient:
m[1,2]=<3
you will modify a whole column.
That's the reason why =< should be used by advanced users only.