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.
I use lots of Photoshop filters. I question whether the i7 and/or the graphic card upgrades @ $250 a pop are worth the incremental performance boost? I plan on ordering 16GB RAM with 3TB Fusion which kicks it up to $2849. I'll have to wait for the Geekbench numbers to see if another $500 on top of that is justified.