I've machined mine to 7kg for now. Weighed in at 9.5 to start with. Will be a few weeks before I fit it anyway but I don't want to be underwhelmed with the difference when it goes on...
Same weight as mine, was a fair difference for me, although I was coming from a dual mass mk4 item.
However many mentioned the lighter pedal feel when swapping out a dual mass, but nobody mentioned any difference for Liveliness, which there certainly was in my case, so I guess it must have made a significant change.
I also noticed that coming off throttle, the engine brake was a lot stronger, less rotational force I guess. This could be classed as a downside.