I had delivery of a new (base model) retina iMac yesterday. All lovely, and worked really well.....apart from sluggish 1990's PowerMac style handling of certain graphic formats, and during certain tasks (Mission Control also judders badly). Some .pdf's in particular sent the beachball into a fury of spinning if I had the audacity to zoom in and try and move them around. After spending a few hours with Apple support yesterday and today (including remote testing by support), finding the same .pdf files worked perfectly well on my 3 year old MacBook Pro and 4 year old PC I've decided to send it back. I did check this forum before purchasing and noted the Mission Control issues reported with the base model graphics card, but thought I'd be able to live with that. What I couldn't accept though was the bad performance of the default .pdf viewer, which I didn't expect. At one stage I thought this might be an OS issue, so tried the same files with Acrobat Viewer, but the same sluggishness and freezing appeared. The test .pdf's were around 4.5mb in size - files under 1mb didn't seem to have a problem, but viewing bigger files seemed to max out the iMac. Considering most .pdf files I work with are considerably bigger than that, I had to call it a day. A real shame as the screen is an absolute joy, but 1990's performance for viewing .pdf's isn't acceptable to me on a £2000 machine, particularly as a designer I'm creating and viewing them on a daily basis. It'd be interesting to hear if anyone else is having the same issue with .pdf's - small files rendered ok, and zooming in via the Finder preview was also fine - though maybe this renders a lower resolution version than the dedicated .pdf viewers. From what I've read on here the graphics card upgrade seems to have less issues, so maybe I'll ensure my next iMac purchase (I still want one!) has a bit more oomph in the graphics department.