I am in the market for the new i7 CTO version because the program I use most, Logic Studio, uses hyperthreading to great effect and will use the eight virtual cores of the i7 vs. the four cores of the i5.
I was at an Apple store this weekend and saw four or five new 27" iMacs, all C2D with the ATI 4680 video card. The i5 and i7 are not yet available in-store or for delivery. One thing that concerned me was that one of the four/five iMacs had a screen flickering issue. I had hoped it was only in need of rebooting, but recently I looked at both the Macrumors and official Mac forums and I have seen mention of it in both forums:
http://forums.macrumors.com/showthread.php?t=808339
http://discussions.apple.com/thread.jspa?threadID=2212682
Check out the Apple thread and the guy posts a video of what it looks like.
The "good" news (if you can call it that) is that the other four in-store were okay, only one suffered from it. The bad news is that they were all the same build, so immediately I think it can't be traced to a certain configuration (i.e. all models with video card X or CPU Y are affected).
I have to admit I'm getting a bit gunshy on the new iMac because of this. I'm hoping that the fact that the i7s aren't shipping until November, and will have a different CPU and GPU (ATI 4850 vs 4680) will make them not susceptible to this problem. I think I'll hold off ordering the new iMac until the Quad Core i5 and i7 are in the wild and people start reporting their experiences from it.
Kind of bummed out, I was hoping to give myself an early Christmas present...





