How's the stability in the DP? (more specifically related to any kind of data corruption, etc...)
I've loaded up Xcode 6, and iOS 8 from our dev account but haven't had the nerve to try OS X 10.10 yet.
The 10.10 Developer Preview is a fairly buggy, and I think your results may vary. So far it seems to be working pretty well apart from the Finder and Safari crashing more often. There are some small bugs here and there, especially with the newer features. So far my MacBook Air has been handling Yosemite very well I think. I'd install it on an external partition, or back up your files first before installing.