Yo, McLaren's unreliability is all McLaren's & Kimi's fault. If they'd slown down since the first seasons race, Kimi would be the world champion, and he'd not be the fastest one.
But as McLaren saw Renault gaining points, they went desperately fast to win them, they saw Kimi and Montoya breaking their cars race rear race and McLaren putted more speed in their cars, when they had to slow down and just END THE RACES IN THE PODIUM.
In fact, McLaren isn't really a better car than Renault (or at least, it wasn't in the 1st half), but McLaren got that 1 second by lap faster by forcing their car (something that Renault did in the 1st season half, when they were 1 or 2 seconds per lap faster than McLaren), and as Renault saw Alonso had a great advantage over Kimi, they relaxed the motor revs and made their car a second slower. They knew that in the 2nd half it'd be near impossible to win a single race due to McLaren's desperate fight. An example: France 2005, alonso 0,5sec per lap slower, but he won due to Montoya's crash (or something, i dun't remember) and Kimi's motor failure on friday's practice.
Kimi hasn't won the championship due to McLaren (and also some errors made by Kimi), they would have ended every single race of the season if they'd have been more clever.
Anywayz, I still think Alonso has been the best driver in ALL the aspects (fast on 1st half, relaxed and waiting to win the campionship on 2nd half). And Renault, as the best team (Briattore sublime, he has drove Renault to driver's championship, lets see now what can he do in the next 2 races to win constructor's championship).