Well, I actually just started riding. I mean, REALLY just started riding. I've only been riding for about 3 months and 600 miles... but I've been reading and participating on a few KTM, moto, and dual-sport boards, so here's my take on the F650.

Before I got the Duke I was actually looking everywhere for either an F650 GS or CS. The Dakar is more suited for off-road riding than the GS (of course). Compared to the R1150 GS, I don't think there is going to be a huge difference... possibly the Dakar may even be better suited for off-road than the R1150 because of it's height and weight. I think the R1150 would be better on road, and is a better compromise between the two... but an F650 GS may be something to consider as well.

Either way, they are both nice bikes. I really like the BMW R1150's. You may also want to look at a KTM Adventure 950?