  The spontaneous interlayer phase coherent (111) state of bi-layer Quantum
Hall system at filling factor $\nu=1$ may be viewed as a condensate of
interlayer particle-hole pairs or excitons. We show in this paper that when the
layers are biased in such a way that these excitons are very dilute, they may
be viewed as point-like bosons. We calculate the exciton dispersion relation,
and show that the exciton-exciton interaction is dominated by the dipole moment
they carry. In addition to the phase coherent state, we also find a Wigner
Crystal/Glass phase in the presence/absence of disorder which is an insulating
state for the excitons. The position of the phase boundary is estimated and the
properties of the superfluid-insulator type transition between these two phases
is discussed. We also discuss the relation between these "dipolar" excitons and
the "dipolar" composite fermions studied in the context of half-filled Landau
level.
