The second significant change appears to revolve around various writing tools. For example, if I compose text and highlight it, Apple Intelligence can give me various options as to what can now be done.
You can change the tone from friendly to professional, and even proofread what you have written. You can also do other things such as summarize key points, or make a table out of the data that you have highlighted. While still an early adaptation, some of these tools can be useful during everyday use, even while text messaging or creating personal notes.
Another change I noticed is prioritized notifications, as in Apple Mail, for example. These will pull out of your inbox what it feels needs the most attention first, and put it on top of the email pile with an Apple Intelligence symbol. Confusing at first, this feature may eventually be more useful with refinements to what it can do.
Overall, the iOS Beta 18.1 feels stable and snappy, and I have not run into any game-stopping issues. You should always take care not to install a beta into a crucial device, however, as problems can and do arise.