I just installed 27.0.1, running Windows 11, and tried editing my first file. I needed to change the artboard size, and it was lagging so bad I thought I didn't click the button. It stalled, then I tried selecting the select tool, and it lagged several seconds. Zoom out. Lag. That was as far as I could stand, so I saved it (took a LONG time for a really simple file) and uninstalled the update. I don't have time for lagging, and my machine isn't laggy.
We are sorry to hear about your experience. We understand how frustrating slow performance issues are. We have consolidated the most popular solutions that help fix these issues. Please check this help article for more details (https://adobe.ly/3cRKo0N).
Also, ensure the GPU performance is enabled in Ai preferences.