However, o1-preview is not a replacement for ChatGPT-4o, which is barely a month old. The new model isn't searching the web or capable of ingesting files and images. Though, that will likely show up at some point.
If biology and math are not your thing, the lighter and slightly more agile o1-mini might be for you, and is also live in ChatGPT Plus now. It's particularly adept at coding.
You can try out the new models in ChatGPT Plus ($20 a month) by logging in and then selecting the model drop-down menu. You'll see o1-preview, and o1-mini have been added to the list as of this story publishing.