Seems to be fine so far, everything I use on Mavericks seems to work. I have it on a Mac Mini (16gb RAM) it does say you need a certain spec to run it.
These are the "known" issues that apple point you to before installing . . .
afari
Safari may hang when playing certain Netflix content.
iPhoto and Aperture
iPhoto 9.5.1 and Aperture 3.5.1 are required on OS X Yosemite. Update to these versions from the Mac App Store.
When entering edit mode in iPhoto, a black screen may be displayed instead of the selected photo.
Photo Stream and iCloud Photo Sharing may not function properly when both iPhoto and Aperture are installed.
iCloud
The shared purchase history page on the Mac App Store is disabled for Family Sharing accounts.
iCloud Drive may appear empty in the Finder after first time setup. Restart to resolve this problem.
AirDrop
AirDrop may not show nearby Macs.
Sending files to another Mac using AirDrop may not work.
I never updated yet as I was worried about all the know bugs and issues. Also that iCloud doesn't update on devices without iOS8
Is it worth downloading the beta?
This is the public beta, so most of the issues were sorted out in the dev versions. As for if its worth it depends if you mind the odd weirdness creeping in.
I dont sync much between my devices using iCloud, but I think when iOS8 comes out I will do more.
I updated to this but then took it back off again. Really don't like the graphics on it. Was far too much of a change for me at the moment. Think I will wait until the final version is released