Downloaded Yosemite public beta, and install on my 2nd partitioned HD on my 27" iMac model 2009. First impression after 24 hour use:
1. visual appearance much more pleasing than Maverick, which I like.
2. no issue during installation.
3. feel much more snappier than Maverick.
4. migration assistant works well too, to transfer the apps.
I should say so far so good.
Looking forward to official Yosemite release this fall.
Word of caution though! do not install in you main working partition drive for this public beta osx. Better be safe than sorry.