After playing for a bit, I've come to the conclusion that I really don't like the new spy system anymore.
While I have nothing against the concept, the implementation makes the game one sided.
It all essentially boils down to this: Can you afford to make more spies than your opponents?
If you can, you have a quick and easy way to cripple your opponents' economy. And with their economy crippled, they don't have the resources to nullify your spies, so you can send them into a death spiral.
If you can't, then you essentially spend ALL
of the spying budget you can afford in nullifying enemy spies so you can maintain some semblance of an economy, and you have to sit there watching enemy spies cripple your civilization.
Of course you can't counter their spies because your economy is crippled, so you can't afford to nullify their spies. Now you are in a downward spiral.
In addition, since the spies are all spent nullifying other spies, your ability to spy on other nations is severely crippled
It just seems to be a bit too powerful and too unbalancing - and too distracting from the rest of the game. Instead of focusing on what I want to focus on, be it technology, culture, economy, or manufacturing, instead I have to focus my resources on getting those pesky spies out.
The game just degrades to a spy war most of the time. I'd much rather concentrate on more important things.
I'm not saying remove the spy system completely - just re-think it a bit.