morsnow,
I have 2009 600 Dragon Switchback, only 300 miles so far, here is what I've seen.
The first 150 miles or so were in the mountains in colorado. Off trail it did just fine got me where ever I wanted to go with out getting stuck, but if I did the mountains again I would change out to wide skis and a 2" paddle track. The 600 was a little poochy for the high elevation but back down to the flat land I was more than impressed with the engine/power. I learned that if you go out west you will have fun on it (switchback) but maximum smiles would be obtained with a 7 or 800 rmk.
On trail the sled hooks up really good, only grip so far has been cornering where I've got a little more dial in to do. (I like to ride the trails "very aggresive but in control") My sled has the ryde fx 2.0 air shocks and I just ordered the pump kit to adjust my ski pressure. I also tightend up the limiter straps and that helped a ton. You will want to swap out the stock carbides for at least 6 inchers if not more. If I can't get it dialed in the way I like I will look into aftermarket skis myself. For general purpose the stock skis are fine.
As far as economy I've been burning oil a little less than 40:1. I had the dealer check it out and they said it is right on but I may adjust myself as I don't see the need to have it that rich. Dealer also told me every sled will be different (as far as oil consumption) which I take that statement as a crock. Also, the computer supposedly has performance restricted and oil use increased during the first 350 miles or so.
I have noticed mine has started to wake up a bit in the last 50 miles or so.
Top speed was 96 stretched out on the RR grade. I didn't pay much attention to fuel economy while out west but on the trails here fuel economy has been poor at 10 mpg or so but I was on a lot of RR grade and lakes during the last trip and keep in mind I always get 1mpg less than everyone else just due to my riding style. My guess is under normal trail riding you will see around 13 mpgs.
If your strictly worried about fuel and oil economy then buy a 600 etek.
The biggest plus has been the ride of the suspension, way surpasses my old edge (which I thought rode great). My back definetly says yes!
Overall a great sled, plenty of performance, the ripsaw hooks up great. I notice the front end on the 10s are a little different for improved boondocking. Not sure what shocks you get but get the pump kit if it has the air shocks. and you may have to do a little tinkering on the suspension to get it to ride to your liking. I would say go for it, a great sled if your into mainly trail riding and want the ability to boondock as well.
You will also want a skid plate if you boondock, handlebar riser and hooks if not equipped, high windshield if staying warm is more important than looking cool, and definetly the rear tunnel storage bag, I opted for the standard IQ bag to leave some room to strap a gas can or ice fishing bucket to the tunnel.