Well, my involvement in spying comes to checking up on the progress of the AI, and directing deep cover missions where I need them. The AI itself seems to do and AWESOME job with spying, depending on my government and race of course. I get enemy tech every few months or so, and most of my research comes from my enemies, at least in the Pestulon AAR, in which the researching ability of my pirates is minimal. I also seem to be getting a lot of "super area weapon" tech in many games, which doesn't do much for me, probably more functional in ROTS.
So, all in all, I don't find spying overpowered, and it's actually a cool feature of the game. It'd be cool if they add even more spying missions in the future, like assassinate leader, capture enemy spy and gently "convince" him to join our cause and be a double agent, incite revolution and/or government change, steal ship and stuff like that.