  We advocate the step change in properties of discrete $d$-level quantum
systems, between $d=2$ and $d\geq 3$. Qubit systems, or multipartite systems
containing qubit subsystem, are exceptional in their relative simplicity. One
faces a step in complexity in valuating measures of quantum correlations for
qutrits and then other higher dimensional qudits. There is a growing number of
arguments leading to such conclusion: recently found no-go theorem for
generalization of the Peres-Horodecki's PPT criterion \cite{sko}, change in
geometry of state spaces of qubit and higher degree qudits (the so called
'generalized Bloch ball' is not a ball anymore), restricted possibilities for
diagonalization of correlation matrices for bipartite systems, more difficult
way for handling the set of relevant families of orthogonal projectors.
