I think the true 'GS'ness of these bikes is a bit of a nonsense. Neither of them are true offroad bikes - yet both bikes will take you round the world no problemo, spoked wheels or cast, GPS or maps scribbled on the back of scraps of paper.
The 12 is building on the cult success of the 1150 - and looks like its doing it very well. For me personally (1150 owner, and never even ridden the 12 yet) - I quite like the look of the 12 - and definately like the idea of the extra few bhp's and the weight reduction etc. I'm also swayed by the fact that every one who has ridden them seems to love them. Definately turned off by ABS / Servo / Canbus / BMW only Serving / Special tools etc. Also, to my mind, the 12 lacks the presence of the 1150 and does seem more plasticy - but hey ho - the world moves on. The question is - will I buy one?
To be honest, probably not (famous last words!). The reason is not so much the bike itself, but the manufacturer. The reliability and build quality issues which are well documented on this site bug me - particularly for what is such an expensive bike - but what worries me is BM's complete denial of these problems. To me they are not playing the game. The marketing philosophy BM want us to buy into with the 12GS is go anywhere, rough 'n tough bikers bike etc etc and yet the reality is that the bikes have and do fail and have 'questionable' build quality, but BM seem to be refusing to acknowledge any of these problems (final drives failing? ABS etc failing?) - which is at odds with the whole GS philosophy. At least we all got our rusty fork braces and lowers replaced no questions asked when we had 11xx's! Ducati 999 going wrong the whole time, maybe - 1200GS, no! Have they learned nothing?!
The truth is that 2 years down the line of day in-day out use, I still really love my 1150, and I couldn't bear to part with it yet! It still makes me grin like a tit every time I get on it. In a couple of years time when perhaps I am ready for a new bike - the 12 will definately be on the list but hopefully but that time another manufacturer will have launched a model to rival or even better the GS (which currently seems to exist in a place of its own) as I would love a bike like the GS or better but made by a manufacturer other than BMW.
My (slightly drunken!) 2pc....