I thought so too, until I rode an 1150GS Adventure a few weeks ago here in Tucson. I really liked the idea of the GS and I even liked the styling. When I got to ride one however, I was really put off by what I felt was a tendency for the bike to feel like it was falling into turns on the street. I'm sure it has something to do with the height and weight of the bike, but it was enough to put me off.
In either the current or immediate past issue of BMW ON (official organ of the BMW MOA Club) there is an interesting article on converting the GS to pure street - sort of a BMW GS Motard thing. Very cool. The GS is a fine bike (though mighty expensive!) that should be even better if the reduced weight and increased power is correct. More info at BMW RA site - see OTL INTL link..IF you can stomach the so called "editor in chief". Occasionally he can make KPAUL look rational.
I also rode a 2004 R1150RT on the same day I test rode an 1150GS. The RT did not exhibit any of the surging I had heard about in the oilhead engined bikes. I was told the problem had been solved with the "dual-spark" engine mods applied to the 2004 model. I don't know if the 1150GS model I rode had the dual spark engine, but I would guess the 1200GS would.
I got to ride the GS extensively, though never owned one. It feels very different from other bikes, but after a couple of miles I got used to it, and started taking turns like there's no tomorrow, surprising lots of gsxrs and cbrs. It holds a line like a freight train, and has lots of power - and you don't need to gear it too much. As a city bike, well - it's no scooter.
also - i'm 6'2, which probably helps. It is heavy, and the shaft drive also requires some adjustment.
The 1200 GS not only has dual plugs, they are electronically controlled to fire separately based on engine speed, etc., which is supposed to alleviate the surge as well as make the engine able to handle lower-octane gas without pinging. The engine also has counterbalancer to get rid of the "boxer buzz," though I have never found vibration to be a problem on my R1100R (OK, it vibrated like crazy for the first 5,000 miles, but not any more...). The bike also weighs about 70 pounds less than the 1150GS, which should make a big difference, even bigger than the advertised 15 extra horsepower.