What aspects of PHP 8 might cause you doubts or inconveniences in use?

Some aspects of PHP 8 that may cause doubts or inconveniences:

• New types and strict typing: the introduction of union types and improved typing require more careful type control, which can complicate maintaining old code.
• Attributes: a new annotation system that differs from the usual comments, requiring adaptation.
• Match expression: more strict and powerful, but different from switch, which can be confusing.
• JIT compilation: improves performance but does not always provide the expected boost and can complicate debugging.
• Changes in function behavior and warnings: some functions have changed behavior, which can lead to unexpected errors in old code.

Overall, transitioning to PHP 8 requires careful study of new features and potential pitfalls.