From what I understand, in '05 the surging problem was essentially taken care of with the introduction of the dual spark system. Many people claim that earlier years can be "fixed" with the use of a hotter spark plug (the electrode extends farther into the combustion chamber). There is info on f650.com, I only scanned through it briefly, and don't remember all the details.
No major re-design in '07, but MSRP is up to $8200, add in heated grips, ABS (which works insanely well), and 4 way hazards, you are closer to $8700. '07s are on the street, but make sure that it has the latest program, there is a TSB out for the earlier program. Supposedly better power and economy with the latest version. Dealer will have the info. There is no centerstand option on the Dakar, but Touratech builds a aftermarket stand.
Power is acceptable for a 650cc thumper. It is no speed demon...but hey, anything that gets 70mpg is not likely to win any races.
Vibration isn't too bad at speed, but you can tell it is a single when you get them above 65mph....you can forget about figuring out if the white car behind you is a cop or not. At 100mph, you can pretty much forget about seeing if ANYTHING is behind you (but the bike handles pretty well at that speed).
About 50% of people polled (at f650.com) think the seats are mid-evil torture devices. I agree, you may not...but be prepared to be looking for a new seat, just in case.
Cross wind is a **********, even on the GS, I imagine the dakar is the same, maybe worse. 424 pounds of fairly tall bike gets blown around quite a bit. High wind nearly put me into a cliff on Mt. Lemmon a week or two ago.
Front shocks are lacking. I have read more than one report about failed shocks when the bikes get loaded down and worked hard (RTW type stuff). Even the aftermarket stuff has been known to fail.
My first impression off road was that the bike was top heavy. The Dakar would be even more-so. Take that with a grain of salt, as I have not spent any time off road in 10 years or so...and even then, it was on smaller dirt bikes (250 and 350cc). It is about 100 pounds heavier than other 650~ish cc dual sports. That is alot of weight to keep upright in technical terrain. Of course, better road manners are the benefit....IMO, this is more street bike than dirt bike.
More opinions later....I gotta get up early.
