Worried about upgrading and was wondering if anyone had tested it yet.
Upgraded from an older 4.6 beta and my static fonts were all messed up, but aside from that it was a smooth upgrade with no other issues… for the first 20 minutes or so I used it. After that time I started getting warnings about memory usage when Unity is open. No such warnings when using 4.6. I’m on a MacBook Air (Mid 2013) with 4GB of RAM. I’ve done some looking around and many people have similar memory issues with Mail, Safari, etc but I never saw this warning until using Unity 5.
Edit: Did a restart and memory pressure is okay so far. Unity actually doesn’t have a huge memory footprint so I’m not sure why I was running into that problem earlier as nothing else was open.
Two things I’ve noticed in Unity 5 are that UI objects sometimes won’t save scene hierarchy updates and the Button component has a new drop-down box that defaults to “off” so a lot of my buttons didn’t work anymore until I set it to “All” or “Runtime only”.
The os itself feels sluggish, plus development builds on U5.
You definitely not on express lane…otherwise everything seems to work fine.
The beta is gives me the motivations to setup another development environment on 10.10 
PS : testing on a separate spare hardwares
No problems here with Yosemite on an old 2008 Mac Pro and Unity 5b9, although I haven’t exactly tested every aspect of Unity yet.
I tried the beta yesterday on a Mid 2013 MacBook Air with 8GB RAM. Feels somewhat slow and I also got memory warnings on a very simple scene with just some cubes and an emissive material. Each time I got the warning I restarted the machine and after a couple minutes playing around with the emissive values the memory warning reappeared. Later I tried on my Windows machine and everything was fine, so I assume it’s an issue with just the Mac build.
Mac Pro Retina, 16GB, 10.10.
Speed is good here; nice and snappy. A few minor issues found and reported with U5 but nothing Kaboom-able. Quite a bit of debugging U4 scripts but I kinda expected that.
In Mavericks I had issues with slow framerates in the Editor - especially when my scene/game views were on secondary monitors. This isn’t an issue at all in Yosemite as far as I’ve seen.
I haven’t noticed any other issues with the editor itself, but Asset Server doesn’t seem to run in Yosemite for some reason.