also note that automation 'response time' will change depending on your audio buffer size. so if you're running out of CPU and decide to extend the buffersize of your soundcard, rapid automation may start sounding tiny bit different (in realtime playback, anyway). not sure if any daw is _not_ a victim to this.
I have never used logic but it does have an option for sample accurate automation, perhaps it is fixed in logic?.. seriously sample accurate automation (or just predictably accurate automation, IE never changes with latency) is my #1 cubase request right now.