Die hard fan of anything doesn't overide commonsense.
In the end, we know nothing, MS and Brawn are smart guys, MS has a 3 year contract, and he has a habbit of making people look like idiots, so come back with your opinions after his next retirement and we'll see how 2010 panned out in his full mercedes career which hasn't gotten off to a good start, but present and past performance is no indication of future success, had MS set his valancia fastest laps in the first 3 races and in china no one would of said anything, the signs are there, the team isn't together. And Rosberg hasn't won a race in his career, Trulli looked good in 2004, HHF in 1999, Rosberg can't be judged at this early stage either, I'm a long term thinker, in f1 where webber has been written off, along with Button, who have won ttitles and races and resurrected their profiles, it would be silly to jump to conclusions on MS, it's smart to wait out, rather then rush in talking about a team and a driver that hasn't told us much about their issues, who are we compared to Ross Brawn and MS.
His fasest laps in Valancia came after a late pitstop (read light fuel load) on new tires. Long term thinker or not, the odds are that at the end of what ever session it is, Rosberg is a great majority of the time faster. That is not down to the car which now is supposed to be to MS's liking (ie long wheel base) as they both use the same equipment.
Your arguement was that the car was a puzzle that even the team that designed it could not figure out. My point is that Rosberg has done a better job in figuring it out than MS...Saying "if you put him in the best car of the grid he would look better" is fan boy logic as it would apply to everyone...and given the RELATIVE performance, Rosberg would use it better.
Besides, what makes you think if MS can't handle Rosberg who, as you have pointed out, has not won anything at this level, he could handle Vettel or Webber?