What I've found about fcpx's sluggish

when working with video with audio channels files:
1. set the timeline to display audio waveform only
2. import all the clips you want
3. select all the clips from the bin and put them on the timeline
4. wait for all the clips' waveform generated, please be patient, it will cost a lot of time!
5. do not enable or disable the audio channels in the inspector, or the audio waveform will generate again!
6. so if you do not want the audio channels, detach them using apple+shift+g, and delete these audio channels
7 generate proxy file after the waveform is ok! or it will be very very slow to make the proxy!

Apple should solve this issue, why should I cost lots of time to make waveform?
It will cost about at least 1/3 times of your clips to make the waveform, when I use a Promise 8Gbps RAID!
If you have 4 hours timeline, you should wait more than 1 hour!

another easier way is:
1. you don't have to wait fcpx making waveforms, just quit fcpx and then restart it.
2. hide waveforms
3. make the timeline thinest!
4. do not show audio inspector!
5-7 the same as above!

I always use Control+Shift+S to detach audio. I believe that the Command+Shift+G camp and the Control+Shift+S camp should have a war. THERE CAN BE ONLY ONE!

The other thing is markers. If you have lots of them in your timeline and don't need them. Select them all in the Timeline index and delete them.

Makes a big difference.

And I don't know if Apple sollve the waveform issue, will fcpx still be sluggish when zooming timeline with 2500 items or more?
So, maybe the bad timeline performance is another issue!