I've been using official CM11 for the past 24 hours just to see what the most recent builds were like (the early builds werehugely unstable.) My impressions are that it's faster and smoother than OmniRom 4.4. I don't think it's placebo either. As far as I can gather, the official OmniRom builds are using older branches as the newer ones are breaking Nexus devices. I assume CM11 is using newer branches as the speed difference is very noticible. It's really nice to use. Also, it seems to have more features than Omni, though this may simply be that I've been using OmniRom for so long that CM's unique features are instantly noticible.
I haven't had any flickering so haven't had to disable HW. There's blue screens, but as most of us are aware, this isn't a rom issue but a kernel one and will hopefully be sorted when 4.3 is released.
There are bugs though. I can't get GPS or location to work. Everything is switched on but my location cannot be found. For me it's not a big one, and it may be device specific, but it is worth considering. Also, the battery is...well... inconsistent. Last night between midnight and 4am my battery dropped 40% while my phone was supposed to be asleep. I charged it again this morning and while it isn't as good as OmniRom, I'm currently on 77% after 4 hours. So yes. Battery inconsistent. Also, I had problems syncing with Google. Wouldn't let me when I installed the ROM, woke this morning to find it synced. A bit weird.
What else... I haven't had to flash superuser. Which is good. I also don't think that I'll have to reflash Gapps on each update. I'll find out tonight.
To summarise, it's a very fast ROM with a few bugs. I'll be interested to see what OmniRom is like on the new branches.
LG Nexus 5