  We discuss various aspects of resummed chiral perturbation theory, which was
developed recently in order to consistently include the possibility of large
vacuum fluctuations of the ss-pairs and the scenario with smaller value of the
chiral condensate for N_f=3. The subtleties of this approach are illustrated
using a concrete example of observables connected with pi-eta scattering. This
process seems to be a suitable theoretical laboratory for this purpose due to
its sensitivity to the values of the O(p^4) LEC's, namely to the values of the
fluctuation parameters L4 and L6. We discuss several issues in detail, namely
the choice of `good' observables and properties of their bare expansions, the
`safe' reparametrization in terms of physical observables, the implementation
of exact perturbative unitarity and exact renormalization scale independence,
the role of higher order remainders and their estimates. We make a detailed
comparison with standard chiral perturbation theory and use generalized ChPT as
well as resonance chiral theory to estimate the higher order remainders.
