I currently own both, but in their non-adventure versions. I've had the 1150 since 2003 and I'm still happy with it. In fact, I was planning to spend some money improving it with new Olins suspensions, LED illumination, a new saddle and an Akrapovic exhaust, as well as fixing some small dents and other many little details. However, destiny had other plan and made me try the new 1300, and despite its high price, I fell in love immediately and bought it.
I had never tried previous intermediate versions, 1200 or 1250, so the leap in performance I noticed was immense. This new model is way better than the 1150 in every single aspect and much more fun and easy to ride.
Oddly, I'm not yet mentally prepared to sell the old one, lot of memories and can't expect a decent money for it. I still use it on daily basis for my work, which usually requires 30-40 kms displacement per day on roads around my hometown. On the other hand, it hardly makes sense to keep them both. I don't know, probably is time to move on. Now, I also like the new F 450 GS and it seems to me a good candidate for replacing the old 1150.