I usually play with pirates off. It's an interesting feature, great in principle, but it brings surprisingly little to the game. Frankly, I find the bidding wars every 15 minutes do more to slow down the pace of the game, and this is a game that's slow enough as it is.
Pirates are too predictable to be dangerous. You know where they're coming from, who the target is, and you usually can predict where they'll hit, and even a small fleet can usually mince them nicely. This makes them less of a danger and more of an annoyance. Short term burden for a long-term experience advantage. I like the feature in concept, but its implementation is lacking.
Personally, I'd like to see pirates launch smaller raids at unpredictable intervals, and intelligently target undefended targets, running away when reinforcements arrive. They should prioritize (and re-prioritize) their attacks as bounty is awarded. The more money on the table, the faster pirate raiding parties spawn. This would mean it wouldn't just become a frantic bidding war once every 15 minutes. You could shell out 5k and expect over the next few minutes for dozens of pirate raiders to depart for that player's world.
