Alright, one last update while I await engineer's feedback:
Cloned the system drive in the imac to my macbook's, and guess what?
With this release, my macbook is unable to negotiate a gig link!
Something is seriously wrong with the release shipped with these macs...
My network util also reports 0 packet loss/error on my 100Mbps (eth0) connection...and as I've said before generally the connection is solid. So I'm inclined to agree that this is likely to be a software issue. Can't decide if I can face the unplugging, packing, driving to mac store and explaining problem scenario..... I can already hear the replies I might get "well its gigabit but only if you use switch x with firmware y with gold-plated cat200 cables...yada yada. ....just a guess, never owned a mac before but generally (in the UK at least) retailers/manufacturers rarely like to take responsbility for their products when they don't work as described...
Made a trip to bestbuy, with one of my switches. Plugged it in and noticed it got a gig link right away. So, I ended up returning my iMac, replacement came in today, I'll let you know what happens when I plug it in after work.
Please do not insult myself, or anyone else in the forum that way. I am going on link speed detection only. If you lose a link state upon enabling gigabit... that is a problem... this is not related to data transfer speeds.