OSX Yosemite performance on a mid-2010 mac mini (NVidia 320M) reminds first 10.0 version : text rendering is 3 times slower (slow redraw when resizing windows), OpenGL is 2 times slower, and user interface test is 10 times slower ! Also opening windows (files listing) is slower, while the new UI theme shouldn’t require more power (it should be faster as it is simplistic – Googlish / Windowish -, without all previous refinements that ultimately landed into Mavericks, not mentioning still non fixed firewire disks sleep issue and trim issue).
Then Apple may use some new OpenGL 4 only APIs for Quartz, while older macs only support OpenGL 3.3.
The new mac mini have half the CPU cores than previous ones, do not allow adding RAM, and only provide an Iris graphics chipset (Iris Pro would have been at least required). Also new imac’s Nvidia 750M graphics card is old.
We now then have to either buy a retina imac ($2500) or mac pro ($2999), or wait for upcoming Broadwell based hackintosh (that will offer same performance for half power requirements, and then will allow smaller enclosure). Also Intel will release an updated Iris Pro.
We then want Scott Forstall (OS features and design), Jon Rubinstein (hardware leading edge with custom processors – should come with A8x) and Bertrand Serlet (Snow Leopard) back, as new team really isn’t talented (except iPad/iPhone hardware engineering).