I'm also very interested in the G68 upgrade outcome. On a positive note though, it's been a plug and play experience with my G68 and the results are outstanding. Enjoying the music will be my priority for the next 12-18 months.
On a similar note though it is astonishing how quickly things have moved on. Only a couple of years (less than two?) after release, the G68xxV analogue video switching functionality is, for many, obsolete...
I agree that it is slightly surprising that most G-series upgrades require a "major rebuild". However, I'm not convinced that the two-thirds of a G68 replacement suggested by JK could have been predicted three+ years ago when the G68 was on the drawing board. It's unfortunate for those of us stuck in the money-still-an-object "mid-high-end" category where kit costs a fortune but doesn't have the hardware flexibility of the true high-end equipment.