For what it is worth..
Since the release of Yosemite I have been testing out LPX with OS X and I have to say the combo of 10.1.1 and OS X 10.10.3 has been pretty well, rock solid and stable for me... The performance hits of the newer OS X versions are still there but Logic's overall stability has been almost as good as my 10.6.8 and LP9.1.5 combo that i use for my main working rig...
So, having said that... what crashes/instability/odd behaviors I have witnessed or analyzed on behalf of others, have all... with very few exceptions, been tracked down to the following causes..
1) Incompatible (with current OS X version) or poorly written external hardware drivers... Digidesign/Avid for example
2) 3rd party plugin issues.... (Update or remove badly behaving plugins)
3) Corrupted or incomplete OS X updates... (Reinstallation on wiped system drive, from scratch of latest OS X and Logic typically fixes this..)
4) Use of conflicting or misbehaving software on Mac.... (Audio Routers/CleanMyMac/MacKeeper are examples.. but there are many more...)
5) Certain versions of Pro Tools and its drivers installed on same Mac (See #1 )
6) Use of Plugins wrappers such as incorrectly configured Novation Automap for example... (See #3 too)
7) Installation and use of 'cracked' software.... be it plugins/DAWs or even LPX itself...
8) Use of Hackintoshs.....
9) Simply User Error.... Setups/Preferences not being properly configured being the most common...
10) Actual Mac hardware issues like a faulty memory chip or Graphic card / driver related issues or SSD/Hybrid chip/disk error issues ..... More common than you would think...
LPX does still have some bugs for sure.. but very few are actual 'showstoppers' for most people these days... There are still some missing features from LP9 that i do miss..... and there are a couple of quirks that you have to develop workarounds for but overall, it's not too bad if you have the right Mac/3rd party hardware.
For example, I have just finished work on a 47 minute score for a Cartoon TV show... that used 80+ mixed audio/Software instrument tracks... in LPX and I had no instability or crash issues at all throughout the three weeks it took to work on this project. (Note: I didn't work with Video... just storyboards 🙂 .)
Other's experiences may well be different but thats how things stand from my viewpoint....