I f you are considering the investment in a new iMac because your pre Retina MacBookPro is too slow think about investing in a new SSD instead.
I have my new SSD from Samsung since yesterday and I am so happy with it.
Everything runs so smooth and fast.
Especially the preview rendering of Lightroom is so much faster.
When I heard about the problems ordering the new iMac I had a quick look at the specs of it.
The CPU of my „old“ Mac Book Pro is not too far away from the one in the new iMacs.
So investing 2400€ in a new iMac that would be probably delivered in 3 month was not so attractive than investing in a new SSD.
My Hard Disk has problems too so I had to buy a new piece of hardware anyway.
8 GB RAM and a 2.1 i7 Quad Core CPU seems good for most of my software. Especially Lightroom has more problems delivering the data than processing it.
My hardware dealer did the math: It took probably 1-1,5 seconds to display a 5D mark II photo on the screen with my old hard disk. The new Samsung SSD should take probably 1/4 of a second. I guess it is faster now. And I don‘t have only 250GB SSD build as a fusion drive. I have the old amount of 500GB as solid state disk build inside.
Not forget to mention the noise: It seemed that the old hard disk was responsible for the fan running like hell. Everything is so quite.