Panel answer: the ability to run code after loading just the first bytes of a module — streaming compilation — plus tree-shakable modules that load only the code pages actually need, yielding a huge performance boost at runtime. Illustrated by the LinkedIn case study: Yehuda Katz rewrote Ember's Glimmer engine in Rust, compiled it to WebAssembly, and measured 0.3–0.5× better initial load time vs the Preact-based rewrite.