So far, Salesforce has a strong record with its larger acquisitions — ExactTarget and Demandware. Their record with mid-sized ones seems more mixed, but that’s what you’d expect. Mid-sized M&A is the toughest category ($200m+ or so) — they have trouble scaling on their own in such a large company, but are too big to just roll into another division. But the Very Big Ones have already achieved true escape velocity.
Odds are, they’ll manage this well with Mulesoft, too. Mulesoft depends more on Other People’s Platforms than most categories, which adds some inherent tension to the offering. But Salesforce has already thought through that.