Oh well, it does not really work as it turns out now.
Espionage(Helper) now hangs and freezes a lot of applications almost every time I start it. This is what happens:
I invoke Quicksilver, I try to start Espionage. It comes up saying: "waiting for EspionageHelper". A few moments later the black password prompt comes up, but before I can type my master password another window appears: Quicksilver wants permission to access one of my Espionage folders (which are are all unlocked already, btw). After that I cant type anything into either of the windows, Quicksilver freezes, Spotlight freezes. I have to start the activity monitor via the Finder (which still responds fortunately) and kill both the Espionage and the EspionageHelper process to make my system work again.
To be honest, I'm not too thrilled so far by my experiences testing Espionage.

Here are the relevant lines from my system.log:
Apr 15 11:02:51 Macintosh /usr/sbin/spindump[1214]: process 302 is being monitored
Apr 15 11:02:51 Macintosh diskarbitrationd[45]: Quicksilver [302]:45827 not responding.
Apr 15 11:03:14 Macintosh EspionageHelper[1209]: INFO: Posted alert message: Denying access
Apr 15 11:03:14 Macintosh [0x0-0xa00a0].com.taoeffect.Espionage[1206]: 2009-04-15 11:03:14.753 EspionageHelper[1209:4203] INFO: Posted alert message: Denying access
Apr 15 11:03:14 Macintosh [0x0-0xa00a0].com.taoeffect.Espionage[1206]: [iSpy.framework] ERROR: send: Bad file descriptor
Apr 15 11:03:14 Macintosh [0x0-0xa00a0].com.taoeffect.Espionage[1206]: [Messages] WARNING: sendMessage: error sending data
Apr 15 11:03:14 Macintosh [0x0-0xa00a0].com.taoeffect.Espionage[1206]: [iSpy.framework] ERROR: error sending message to ispyd
Apr 15 11:03:15 Macintosh [0x0-0xa00a0].com.taoeffect.Espionage[1206]: "disk3" unmounted.
Apr 15 11:03:15 Macintosh [0x0-0xa00a0].com.taoeffect.Espionage[1206]: "disk3" ejected.
Apr 15 11:03:15 Macintosh EspionageHelper[1209]: WARN (dmgDetach:264): couldn't unmount using cocoa, trying lower
Apr 15 11:03:15 Macintosh [0x0-0xa00a0].com.taoeffect.Espionage[1206]: 2009-04-15 11:03:15.915 EspionageHelper[1209:10b] WARN (dmgDetach:264): couldn't unmount using cocoa, trying lower
Apr 15 11:03:17 Macintosh /usr/sbin/spindump[1214]: process 302 is being no longer being monitored
Apr 15 11:03:19 Macintosh [0x0-0xa00a0].com.taoeffect.Espionage[1206]: "disk4" unmounted.
Apr 15 11:03:19 Macintosh [0x0-0xa00a0].com.taoeffect.Espionage[1206]: "disk4" ejected.