Just do it with caution 🙂
How I did it (Public Beta):
- Backup with Time Machine
- Clean install of Mavericks (My 'other' storage went nuts so non-Yosemite unit)
- Backup back
- Make a partition
- Install Yosemite on partition
- Launch Yosemite
- Download a few essential apps (uTorrent, VLC, Telegram and iPhoto in my case)
- Have fun
It works amazing for me, it's actually better than Mavericks. Sure some bugs, but I report it and that makes me feel useful. I'm really happy that I can help Apple as a regular consumer, make the product even better. But I've thought about it for two months, did my research and found this forum. Since the day I installed Yosemite I've been reading every post, keeping up to date so I know what to look out for and how to fix things.
But the biggest thing you see is that the beta experience is different for everyone. So be prepared for any situation you think is applicable for you. 🙂