As I've argued in the race thread of Barcelona already, Maldonado had pace all weekend. Still, in normal circumstances I'm almost sure Lewis would've won the last race, but Maldonado didn't come from nowhere only because of his tyres. He was fast in practice, in Q1-3 on single laps and he was very fast and consistent in the race, compared to Alonso and Kimi, two drivers that also enjoyed a lot of free racing space. Fair play to him and it isn't any more or less a tyre victory because it happened to be a Williams car and driver combination that won the race this weekend.
That said, I'm not sure about the tyres. They are very important and I think, although I'm not decisive on the issue yet, that they are too important as of now. I don't know if its the tyres fault though. It's clear the tyre handling is extremely delicate, so a perfect setup is needed for a consistent race pace.
But aren't the tyres also becoming a lot more important because of the strict regulations this year? One can assume that teams with similar budgets and know-how all know how to make a basic car. For some (Ferrari this year) it might take a bit longer than for others, but they will arrive there or there about. At the moment, there is no way (or teams didn't find a way yet) to develop a competitive edge, so when all cars are roughly the same, we see circumstances dictating race results. Tyres play a role in it, as cars do seem to heat up the tyres in different ways, and the fact that we see such erratic performances from some drivers and such differences among team members (Senna vs Maldonado or Alonso vs Massa, Button who is very fast in some races and dreadful in others) might indicate that it is not the car that makes the difference this year, but the driver. Interestingly, the faster drivers in qualy also seem to be the faster drivers in the race (apart from Williams having a better race car than a qualifying car in general this season and Mercedes vv), indicating that the tyres will last when you treat them right (i.e. by driving fast). It is once they are abused that they are going like crazy, whether it's due to following other cars, dirty air, locking up, lack of balance or most likely a combination.