I love the Sertao. It's comfortable and smooth enough to ride all day, other than the seat, which will be addressed in time. Offroad, it has really surprised me with it's capabilities. I always seem to get into way more difficult terrain than I mean to and the bike will get through steep, rough, rocky desert amazingly well. The 4 or so gallon tank is small but I always get 60-65 mpg so the range is pretty good.
I had an 1150 GS for 115k miles and now I think I should have had a 650 the whole time. Other than the power difference this bike will do everything the big bike would do. I don't miss the power and I have always liked big singles.
I do love my K bike too. I'm collecting parts to convert it to paralever right now.
Sorry for getting a bit off-topic.