Yeah. It's not bad. It's good for giving weaker capital ships like frigates and destroyers a fighting chance against monsters like the Vagyr battle cruiser. Defense frigates are somewhat useless. I haven't figured out how to use them properly yet because the field goes offline quite quickly and once you throw them into battle, they're usually the first thing the enemy goes for, and these things can take very little punishment. Mine's are VERY good. They're just as good as they were in the first one... actually, I would say better, because now you're given the option of creating the location and size of the field of mines you want to deploy. However, each ship has a limited supply and you can't just LITTER the enter place with them like you could in Homeworld 1. I think each minelayer is allowed to drop three max. If they explode then the minelayer can make more, but they are only allowed to have 3 ACTIVE mines at once. Also, even though they have a forward mounted gun, they tend to like to just sit around and do nothing in the middle of a fight.
In the end, the best way to to win is just through overwhelming force and constant buildup.