I'm emphatically underwhelmed by the prospect of owning this product. The straps are the best part of the design IMO and having to remove it daily to charge is dorky. I think it's no coincidence that Apple is launching the watch to coincide with the release of the iPhone 6 Plus which is cumbersome. I believe the watch was conceived as an interface for the larger phones. I wish Apple luck with it but I just don't see a runaway hit.
Although the greed motivating this consortium is misguided, their resistance to Apple Pay is an obstacle nonetheless. I'm certain Apple calculated such speed bumps but its stock will probably take a minor hit Monday on the news.
I hear you, Yosemite's response time seems to lag a little. My speculation is the OS will grow speedier as the cache begins to bolster apps. I'd also hope future updates address lag time. I don't believe the lag time is connected to upgrading over Mavericks, I think its characteristic of Yosemite.
Upgraded 27" i7 iMac (2009) and Macbook Air (2010) over Mavericks with no problem. Big fan of Yosemite's GUI. A vast improvement over Mavericks which I always considered in Beta. Neither of my Macs do handoff but I'm getting the i7 Retina 5K soon.