Barcelona away to Sociedad this week, so I think it's a tough challenge for them especially after the goalless match against Vallecano. If Sociedad plays very defensively, I don't think the result will be much different from the match against Vallecano because the tactics used by Xavi so far are not very effective against a team with a good defense, especially if they park the bus.
Of course it is too early to determine who will take the title from Real madrid. Everything are making good performance at the start of the league it doesn't mean it will gong well like that. Most time some teams starts very well in the beginning but has the league continues things change. Their are some teams that will start badly and may improve middle of the league. Real Madrid are too strong to lose the title.
It doesn't matter if the fans are very optimistic about it, but I don't think anyone will be able to draw conclusions only after they watched the first match for the start of the season. Even if Barcelona doesn't succeed in their first match, it won't decide anything at the end of the season.