I'm on an older (4 gig 2008) iMac, with Mavericks, Focusrite Sapphire Pro and Logic X , though I'm really happy
with the quality of Audio and the plugins in Logic -It's become a troubleshooting environment which fortunately I have the skills to circumvent, although -Very annoying!
Aside from certain prominent plugin vendors (not reallly apple's fault) not ready at 64 bit (basically killing my massive orchestra/synthy lib)
I have a lot of audio clocking issues. I always see random cpu spikes, spinning beach balls and even worse- Big Crashes. It may all be related to autosaving? I had one crash where autosave saved nothing! - I had another where it was current - but I'm pretty sure it's also having issues Finding stuff (I had to reinstall Kontakt 5 Player bc it would not find the libraries after a crash)
If the system sleeps (app nap on logic is off) I have to kick the Audio in the butt (usually switch Preferences/Audio) to get it back. This is a result of going to Mavericks. I had no such issues in Mountain Lion.
I just relate this here because I really fdont' think this is a Focusrite issue and Mavericks seems to play nicely with it (do check with focusrite - they updated the drivers in October, but even before that was not an issue) -
i think the issue is with Logic Pro X - new stuff in my logs indicate there are
Audio engine failures- and stuff like this:
11/7/13 6:08:02.215 PM Logic Pro X[60682]: CGContextSetFillColorWithColor: invalid context 0x0. This is a serious error. This application, or a library it uses, is using an invalid context and is thereby contributing to an overall degradation of system stability and reliability. This notice is a courtesy: please fix this problem. It will become a fatal error in an upcoming update.
That's all-
sorry if this is whiney I do send feedback to Apple but fyi...