Yeah, what did happen? This issue had nearly 1200 votes last time I checked.

What happen here this had over a thousand votes?
Hi thought I would give you an update I downgraded to mountain lion and unity and my iMac is running great shan't be updating till this is fixed.
With unity and mavericks it's like wadding through treacle with clogs on

Can someone please tell me if it is safe to Roll back to a previous OS since maverick might be the issue ?

I have a MAC mini and Maverick - and My unity freezes up all the time just for changing the view ?! What should I do ? I have a game that I need to finish ASAP ?! Please help :|

This issue seemed to improve when I turned off App Nap in the inspector for Unity and MonoDevelop. Not sure if it is the complete fix or not.

So anyways (sorry for posting twice) This issue has to be fixed Immediately, i just can't stand it, I have 4GB of memory and when I have unity, safari, and mono develop my memory drops down to only 150MB of memory, if your memory reaches to low as 80MB of memory all Hell will break loose. Anyways to reinforce my 2nd comment guys don't leave so many programs open especially safari witch might be the reason why you guys are having so many freezes

Hey Guys, If you are having performance issues with unity, you should get Memory Clean (it will clear unnecessary data stored in the memory allowing more free space) from the app store, it will help save performance and prevent some freezes and shutters in unity, next you don't want to leave a lot of programs running in the background, especially safari witch uses a ridiculous amount of memory even with a lot of tabs on. don't leave so many programs on or else it will eat up all of your memory, all of this tips REALLY helps save performance and really prevents lags and freezes when I'm working with unity. Anyways Im pretty pissed off about this issue, I assume it must be the Operating systems issue with the program. this has to be something unity may have to solve, or else if they can't, then apple has....

Hey! I found a solution for my Macmini5,2 (OS X 10.9, Unity 4.3.1f1).
look like my hardware’s performance can’t handle well OSX “App Nap” technology, but my “Mission Control” is back to lightning speeeeeed!

Try enable "Prevent App Nap" in both "Unity.app Info" and "MonoDevelop.app.Info”.

Optional setting in Unity application :
Unity > Preferences > External Tools > External Script Editor, Browse.. 'your MonoDevelop.app location'.

Good Luck!

-- Issue with VSync:
Unity should be using CADisplayLink
It's the OSX callback mechanism so Unity apps are driven by the display VSync, rather than trying to render with a CPU timer. This makes redraw timing driven by the display, not the CPU timer.

CPU timers on or near display refresh rate (60Hz usually) causes a stuttering as the actual render happens out of phase and causes a beat frequency to appear. Without looking at the source code, I can't be sure, but it sure looks like Unity is using the CPU timer approach.

-- Issue with GC:
I hear Mono-Develop engine is apparently the old one on Mac, with significant garbage collection performance issues. I would rather take a beta with no GC issues, than a creaky old one, assuming it's stable for most development.

This is a monumentally irritating issue. I just upgraded to Mavericks 10.9.2 beta, which unfortunately had no impact on the problem. I suppose I will try the multi-monitor setup that some people report is working.

...but let's get this fixed soon, pretty, pretty please.