There’s good news and bad news for Apple in the latest projection from Crittercism, a mobile analytics company. Though ultimately, they may both cancel each other out.

With iOS 9, Apple’s latest mobile operating system upgrade, dropping today, the company built a model to predict how quickly people will install the new version.

Here’s the bad news: During the first week, Crittercism believes there will be a 31 percent adoption rate, down from 35 percent from the same period for iOS 8.

Why? In part, because iOS 8 was perceived to be a bit buggy by some, and in general, consumers are growing more cautious about upgrading. “We believe this is because public perception of upgrading has been a bit tarnished,” the company said.

The good news is that according to Crittercism analytics, the crash rate for iOS 9 at this point is 2.77 percent compared to iOS 8.0, which had a crash rate of 3.48 percent at this point last year.

The upshot is that over the following weeks, Crittercism believes this more positive experience will translate into an increased pace for downloads. Crittercism projects that iOS 9 will reach the 50 percent adoption rate in 25 days, which would be three days faster than iOS 8.

Not sure yet if you’re going to upgrade right away? Here’s the schedule from Apple for when iOS 9 will be available.

And our Mark Sullivan believes there are 5 good reasons to upgrade to iOS 9.