I've had a few ARFs myself but none at present. I just don't seem to get very attached to them and when I need room in the shop for more planes to build the ARFs are the first to get sold. I just assembled a shiny new 60 size Graupner Patty Wagstaff Extra 300s ARF just before the Holidays. Very nice quality for an ARF but fairly heavy construction. It was a lovely model and flew very nicely. I put about four flights on it and then was bored with it and so it got sold.

As far as kits being 20% prebuilt, I wouldn't necessarily agree with that. The Sig Senior kit you mentioned comes as little more than a big box full of sticks and a set of plans. Almost the same as scratch building except the ribs are pre-cut.
Same goes for the Sig Liberty Sport that I'm building currently. Big box of sticks and a vac-formed cowl and pants.