I have bought one of the new XT660Rs. Here are my impressions and experiences. Yes I agree - it looks pretty cheap alongside, say a Transalp or Beemer GS. The plastics are horrible and the decals peel etc, etc.
But: I did 1400 miles up to and around Scotland in 6 days and the bike was excellent and very comfortable indeed. 70+mph Motorway speeds loaded up with camping gear - very smooth (for a single) and on single track twisties the handling and stability were a revelation - MUCH better than a Transalp or GS650. It handles mild off road comfortably and feels well balanced. Headlight is superb. Gearbox is good. Engine "feels" flat, but it pulls well and tops out at around the ton. Brakes are OK - nothing special.
I have now done 3600 miles and everything is 100% OK. No oil used. After a couple of top ups before 1000 miles no coolant used. Overall average mpg is better than 70, giving a range of 200 miles. It has been ridden all day on tracks through the Welsh Hills and nothing has fallen off or worked loose.
I appreciate that this isn't high mileage round the world stuff, and only time will tell if it can handle really big trips, but, based on my own experience, I wouldn't swap it for anything in its price range. In my opinion is a better all round riding bike than either the Transalp, GS, DRZ or the KTMs I have ridden. A true all rounder.