Packages can definitely have a significant impact on Atom's performance. You can observe all kinds of events, and binding a slow handler to certain events like text changes and cursor movements can make the editor feel sluggish.
It's important for Atom's extensibility that these kinds of events are provided, because it allows many major editor features to be implemented as separate packages, but it means that naively-implemented packages can really slow things down.
Many Atom packages are pretty new, and their authors may not have put a lot of effort into optimization yet. In the past few months, the team has put a lot of effort into stabilizing and solidifying our APIs. We're hoping that now that the APIs are stable, the package ecosystem will really start to mature.
It's important for Atom's extensibility that these kinds of events are provided, because it allows many major editor features to be implemented as separate packages, but it means that naively-implemented packages can really slow things down.
Many Atom packages are pretty new, and their authors may not have put a lot of effort into optimization yet. In the past few months, the team has put a lot of effort into stabilizing and solidifying our APIs. We're hoping that now that the APIs are stable, the package ecosystem will really start to mature.