Extension members are the headliner. The new syntax enables extension properties, extension operators, and static extension members — all defined in a unified extension block. It's fully compatible with existing extension methods. This is a big deal: you can now attach properties and operators to types you don't own, including interfaces and sealed classes.
The field keyword is the second most impactful quality-of-life change. It allows field-backed properties to eliminate explicit backing fields — the compiler generates the backing field automatically, making code cleaner and more maintainable. Perfect for the "I need some logic in a setter but don't want a manual field" pattern that comes up constantly.
Null-conditional assignment (?.=) lets you use null-conditional operators on the left side of assignments, through constructs like customer?.Order = ....
User-defined compound assignment operators: you can now overload +=, *=, and similar operators. Previously, += w