I wouldn't want to tag the result of the supposed big teams in Italy this weekend "disappointing" because it's just their opening games of the season so, I believe they can bounce back to their bests but they were surprising results considering the quality of players in these teams. Inter Milan's result if you ask me was the most surprising because they led the game in two different occasions but still failed to win but that didn't change my opinion about them winning the league title this season.
You're right. It is just the first match, the draw is also not a too bad result. Inter Milan, AC Milan, and Roma still have a lot of time to improve their game and it is actually interesting result because the race for the title to be more tighter. I'm sure the result of the first match doesn't fully reflect the strength of the big teams in Serie A. They may be just unlucky, or they need time to adapt with the new players. Let's how they will play in the next few matches! They should evaluate it and play better in the next matches.
The Atalanta and Juventus games I don't think will leave us with any shocking result. The two teams I think will win their respective games.
Surprising result is always possible. Moreover both team looks like having a similar quality. I even assume the result of the match can be a draw again. But if Juventus can win this match easily, I can feel optimistic that Juventus has a chance to be the champion this season. Juventus is managed by a better coach now, they should perform well this season.