[PvK]

I think they are useful in situations where your empire has a lot of resources to invest over time, such as peacetime development periods in multi-player games. They are both powerful and expensive, entirely disposable yet with no maintenance cost. They're expensive in the short-term but cheap in the long term, and are the only unit that can be used offensively across warp points without carrying them all in ships. Also, they can make a single ship much more powerful than it appears. So, it makes the most sense to me to stockpile them during periods of peace, and use them for brief but terrible surprise strikes.

Also, if a game is set up so that they bypass mines (in settings.txt), then they are good for that purpose.

PvK