After I'd installed cm-10.1.3-i9300 (http://download.cyanogenmod.org/get/jenkins/42508/cm-10.1.3-i9300.zip), my Wi-Fi module didn't work. I turned it on, entered the password, and it ended up showing me the state Saved.
On http://forum.cyanogenmod.org/topic/79452-samsung-s3-5ghz-wifi-not-working/#entry422420 they suggested creating a file in /data and changing its owner, group, and mode bits.
su
echo murata > /data/.cid.info
chown system /data/.cid.info
chgrp wifi /data/.cid.info
chmod 0660 /data/.cid.info
But it didn't work for me. When I restarted the phone, there was no such a file. I didn't manage to make my Wi-Fi module work and just installed the newest nightly build http://download.cyanogenmod.org/get/jenkins/85875/cm-11-20141003-NIGHTLY-i9300.zip (the link may be dead now).
I tested the Wi-Fi module first thing, and it worked. Then I spent a week to test everything else. Everything is fine. If I notice any bugs, I'll post them here. Besides the launcher looks like the one on Android L.
The only one problem I had to solve was root access via ADB. I found the answer on http://android.stackexchange.com/a/70159/18093
Just go to Settings - Superuser, press the menu item Settings, and change Superuser access from Apps to Apps and ADB.
Afterwards I installed Google Apps: Play Google, Gmail, etc. Just visit http://wiki.cyanogenmod.org/w/Google_Apps, download a ZIP for your version of CyanogenMod, reboot to the recover mode, and install the ZIP. That's all.
In conclusion, there is a little tip which may be helpful to somebody. I found it on http://forums.androidcentral.com/nexus-10-rooting-roms-hacks/257959-downloading-do-not-turn-off-target.html#post2619440
Power-Home-Volume Down = Download Mode
Power-Home-Volume Up = Recovery Mode
I got mixed up the key combinations a few times while installing CyanogenMod.