  We comment on various aspects of the the dynamics of 3d N=2 Chern-Simons
gauge theories and their possible phases. Depending on the matter content, real
masses and FI parameters, there can be non-compact Higgs or Coulomb branches,
compact Higgs or Coulomb branches, and isolated vacua. We compute the Witten
index of the theories, and show that it does not change when the system
undergoes a phase transition. We study aspects of monopole operators and
solitons in these theories, and clarify subtleties in the soliton collective
coordinate quantization. We show that solitons are compatible with a mirror
symmetry exchange of Higgs and Coulomb branches, with BPS solitons on one
branch related to the modulus of the other. Among other results, we show how to
derive Aharony duality from Giveon-Kutasov duality.
