i think the energy mechanic works well. It would be nice to have unlimited energy, but it would also be nice to have unlimited money in the real world. However, having limited resources adds an aspect of realism and forces you to play better so that you win and therefore dont waste your energy. It's a mechanic that gets you into the atmosphere of the game, so i like it.
my only gripe with this game is how it replaces strategy with luck in a few areas. For instance, activated abilites like "Strike" and "Heal". It would be really nice to be able to pick the targets for these abilities. Many a time i have lost a game i could have won simply because the wrong unit got healed, or the wrong enemy got striken. Very frustrating. Otherwise really nice game. :)