Performance and stability are top priorities for us and we're working hard to push out fixes to make Arc faster and more reliable.
If you’re able to identify a specific action or process that directly causes or contributes to the issues you’re experiencing please send us an urgent bug report in Arc (Command-T > type “report bug”) and a trace.
Here’s how you send a trace:
Head to Help > Troubleshooting > Record Trace in the Mac Menu Bar.
In the box, give a quick description of what’s slow and select “15 seconds”, and “Start Tracing”
For the 15 second Trace, perform the action that feels most slow (e.g. switching tabs, loading a webpage, or scrolling). It’ll send us some diagnostics automatically.