1. Make sure only Logic is running. For example, close your email program and browser and all other stuff. 2. Increase your audio buffer in the audio preferences pane to see if that has any effect. The larger your audio buffer, the more latency you'll have. 3. Start with an empty project and add tracks from there instead of one of the templates. See if that makes a difference. Is the processor or the memory the bottleneck? In the transport bar, double click the small "CPU" and "HD" symbols and watch their meters. Alternatively, just open Apple's activity monitor and press [cmd]+[3]. On the gearslutz forum, there's a thread where everyone can benchmark their computer for logic. Here: http://www.gearslutz.com/board/music-computers/371545-logic-pro-multicore-benchmarktest.html

I use Logic Pro but I guess it works the same. Here we go. In the arrange window, press [A] to open automation. Press [ESC] and then press [2] to select the pen tool. Draw points for fade-in and fade-out action. Afterwards, make sure the track mode is set to "read". You can also do this live, by setting the track mode to "latch", then press play to play your project, and make a fade-in or fade-out with the volume slider. Put the track back in "read" mode afterwards. You can adjust your performance by pressing [A] and seeing what you've made.