  Although well motivated from theoretical arguments, the cosmological constant
\emph{barrier}, i.e., the imposition that the equation-of-state parameter of
dark energy ($\omega_x \equiv p_x/\rho_x$) is $\geq -1$, seems to introduce
bias in the parameter determination from statistical analyses of observational
data. In this regard, \emph{phantom} dark energy or \emph{superquintessence}
has been proposed in which the usual imposition $\omega \geq -1$ is relaxed.
Here, we study possible observational limits to the \emph{phantom} behavior of
the dark energy from recent distance estimates of galaxy clusters obtained from
interferometric measurements of the Sunyaev-Zel'dovich effect/X-ray
observations, Type Ia supernova data and CMB measurements. We find that there
is much \emph{observationally} acceptable parameter space beyond the $\Lambda$
\emph{barrier}, thus opening the possibility of existence of more exotic forms
of energy in the Universe.
