I've finished about a dozen missions, and so far I'm mostly enjoying it. There's no story or anything, just a series of battles to complete. You earn gold which you can use to level up your troops or unlock new troop types or increase the maximum "point value" for your army. There's something satisfying about launching your little guys at an enemy and watching him fly off the map (every map is an island, so you can always knock the enemy off instead of whittling down their hit points). And I'm a sucker for any game that lets me level up or unlock things.
No crashes for me, but there are some rough edges and bugs. Sometimes upgrading a unit causes your army's point total to freak out. I've been in situations where I couldn't field any units because it thought I was exceeding the point limit, and I've had the opposite happen: no amount of units would cause the limit to be exceeded.
I played one multiplayer match. It uses your army from the single player game, and I was only a few missions in and was playing against an army that was so upgraded he one-shotted all my troops. So, that's kind of off the table until I play more of the campaign, assuming I DO play more, what with the upgrade bug being such a pain.