I'll be brave and jump into the topic here...
For the most part I love using mines, and the bigger the better. Unfortunately larger mines do tend to take a snails age to build up in any worthwhile numbers, so it's always best to have decent protection in your system(s) already before dedicating any time to build the big boys.
I've discovered though that the Mod you use can change your tactics quickly. Atrocities' Star Trek Mod allows for Space Yard Ships to build ships & units at a crazy fast pace. In a case like this you can build large mines like a mad man and not make any huges dents in your construction que.
So to sumarize, mines are good, but mimes are bad
