Due to a change in the way espionnage works the only way to increase your knowledge of another race is to directly use your agents on one of their worlds.

Frogboy did say that there was going to be a change in that in the final version but seen as nothing has been seen on that side of things in the last few betas i guess it is not going to change, unfortunatly. BTW You can still not spy on minor races either!

Also, placing agents stops production of the building they are placed on. Some buildings (starports and initial colonies) cant have agents put on them, but as far as I know, all the other buildings are fair game. This makes spies useful in certain situations. Attacking a planet? Place a spy on a farm for one turn and billions starve, making the planet easier to attack. Wanna stop a planet from making ships? Place your spies on their industrial centers and they wont be doing anything on the planet fast.

It should also be noted that spies also counter act spies the AI places on you. So if an AI places a spy on one of your planets (a stock exchange for example) you need one of your spies to negate him (note that the AI does this as well). Thus you need to understand when to use your spies for offense and defense. Unless you have counter espionoge centers on all your worlds. Then use your spies as offensivly as you want.

On the flip side, I do like the original espionage system from DL better myself. Perhaps use that with agents preforming their primary function as of now (stopping building production).

Yes, I stated this above.

I have kept up on the game, visiting the galciv2.com many times, even though my gaming attentions were elsewhere.

I know how to use spys to shut down buildings however I did not find it listed anywhere that they replaced the slider bar as far gaining information from your neighbors

If the absence of the slider bar had been in one of the posts I sifted through for my answer, I wouldn't be here posting for some clarification.

Would you like to know more?

Brad mentioned some time ago making a "2.0" update to Galciv, after TA is released I think. He was going to consider allowing spies to be used passively, ie you could assign them to gather intelligence against another empire without you actually having to place them on a building and exposing them to being rubbed out by an enemy agent. I presume we will still see this update at some point in time. Many people have expressed dissatisfaction with the new spy system and Brad assured us that this would eventually be addressed.

This was gone over soooo much when DA came out. There was (to my knowledge) no thoughts of reverting to the old system.

Just a FYI, the things (that I can remember) that changed from DL->DA are:

-Super Abilities for each race
-Espionage system overhaul
-Asteroid mining introduced
-Mega Events now an option for in your game
-Tech Tree consolidation (ex Laser I, II, III etc are all in one segmented block)
-Extreme Planets requiring new techs to colonize

There may be a few others that I have forgotten though.