Infinite Flight 1.6 was just published to the marketplace. It fixes the performance issues that were reported by pilots last week. The update should start propagating in the next few hours.
This update should make the performance even better than in 1.4. In our search for the source of the stutters, we found a piece of code that wasn't really optimized, we cleaned it up, and the simulator now runs even better!
Let us know what you think in the comments :)
We're hard at work on 1.7 now, bringing you more features, and perhaps new airplanes... stay tuned!